Musculoskeletal Disorders Statistics

Musculoskeletal Disorders Statistics

Musculoskeletal Disorders: a group of diverse conditions affecting bones, joints, muscles, and connective tissues, resulting in pain and loss of function. These disorders may result from infectious, inflammatory, or degenerative processes; traumatic or developmental events; or neoplastic, vascular, or toxic/metabolic diseases. Chronic pain and a loss of function are the primary mechanisms through which musculoskeletal disorders lead to disability and work loss.

https://www.ncbi.nlm.nih.gov/books/NBK559512/

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Ankylosing Spondylitis (AS): Defined as a type of chronic, inflammatory arthritis that mainly affects the spine causing chronic back pain and progressive spinal stiffness as the most common features. Other characteristics and complications that may accompany the disease are buttock pain, hip pain, peripheral arthritis, enthesitis, inflammatory bowel disease, and vertebral fragility.

• The US population prevalence of AS is estimated to be 0.9%.
• AS is typically diagnosed in people (more common among men than women) younger than 40 years, with about 80% of patients developing symptoms when they are younger than 30 years.

https://www.ncbi.nlm.nih.gov/books/NBK470173/

Cauda Equina Syndrome (CES): refers to a group of symptoms that occur when nerves in the cauda equine (a collection of nerve roots that spread out from the bottom of the spinal cord) become compressed or damaged. These nerves roots connect the central nervous system and peripheral nervous system. CES can lead to pain, numbness, and weakness in the lower back, pelvic area and legs, drop foot; problems with bowel or bladder control; sexual dysfunction; and even paralysis. As such, CES is considered a medical emergency.

• Herniated disc in the lumbar area is the most common cause of CES.
• CES comprises around 2-6% of lumbar disc operations, with an incidence in the population thought to be between 1 in 33,000 to 1 in 100,000.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3082683/

https://rarediseases.info.nih.gov/diseases/10987/cauda-equina-syndrome

Chronic Low Back Pain: Defined as the persistence of pain in the lower back for at least 3 months, is usually associated with significant emotional distress and functional impairment, and often described as “nonspecific” because a specific cause is rarely identified, and no definable pathophysiologic abnormality is present in many cases. (Hartvigsen et al, 2018)

• Chronic back pain is the leading cause of years lived with disability in the United States, accounts for more than 57 million doctor office visits and 264 million lost work-days per year (USBJI, 2014a)
• In 2019, 39.0% of adults had back pain making it the most prevalent site for pain, followed by lower limb (36.5%); upper limb (30.7%); headache or migraine (22.4%); abdominal, pelvic, or genital (9.8%); and tooth or jaw (9.2%).
• Most likely to experience low back pain are adults aged 65 and over, women, non-Hispanic white adults, and those with income below 100% of the federal poverty level (FPL)
• Total costs of direct medical expenditures and loss of work productivity combined related to low back pain have been estimated to be as high as $635 billion annually in the US.
• Exercise therapies are the first-line treatments recommended in guidelines for routine use in chronic low back pain.

https://www.cdc.gov/nchs/products/databriefs/db415.htm

https://www.cdc.gov/nchs/products/databriefs/db415.htm

Degenerative Disc Disease: Defined as the breakdown of intervertebral spinal discs, primarily located in the lumbar and cervical spine. This breakdown can result in pressure being placed on the spinal cord and spinal nerves exiting the spinal cord. Degenerative disc disease can be influenced by mechanical, traumatic, genetic, and nutritional factors that ultimately results in a loss of cartilage cells and the proteoglycans in the cells of the disc. This is connected to damage of adjacent structures leading to functional changes and clinical signs and symptoms.

• It is reported that initial degeneration of intervertebral discs may be present as early as in adolescence with 20% of young people having mild symptoms of the disease.
• It is estimated that 10% of the male population is affected by age 50 years and that climbs to 50% prevalence at the age of 70 years.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7007629/

Herniated vertebral discs: A condition affecting the spine in which the annulus fibrosis is damaged enabling the nucleus pulposus to herniate potentially causing compression on spinal nerves with associated sensory and motor deficits.

• The incidence of a herniated disc is about 5 to 20 cases per 1000 adults annually and is most common in people in their third to the fifth decade of life, with a male to female ratio of 2:1.
• Disc herniation is more common in the lumbar spine, followed by the cervical spine.
• Over 85% of patients with symptoms associated with an acute herniated disc will resolve within 8 to 12 months without any specific treatments with most cases of disc herniation resolving within a few weeks after onset of symptoms.

https://www.statpearls.com/articlelibrary/viewarticle/20584/

Kyphosis: Kyphosis is an increased thoracic spine curve causing a bowing or rounding of the back. The three main types of kyphosis seen in individuals are postural kyphosis, Scheuermann disease, and congenital deformities.

• Postural Kyphosis: Usually starts to show up in adolescents, is associated with a slouching posture, and is more prevalent in females compared to males. This type of posture is more associated with rounded shoulders and a forward positioned head.
• Scheuermann Disease: An acquired structural deformity that usually beings before puberty and develops into anteriorly wedged vertebral body. The prevalence of this type of kyphosis is about 0.4% to 8% in the United States, with males being twice as likely to have it compared to females.
• Congenital Kyphosis: An uncommon but severely disabling, rapidly progressive kyphosis that is commonly associated with neurological complications.

https://www.ncbi.nlm.nih.gov/books/NBK558945/

Lumbar Lordosis: Lumbar lordosis is an excessive anterior/inward curvature of the lumbar spine (anterior pelvic tilt) often caused by an imbalance between muscle groups surrounding and acting on the pelvis – tight hip flexors and low back extensors, and weak trunk flexors (abdominals) and hip extensors. However, there are other causes of lordosis including spondylolisthesis, congenital lordosis – achondroplasia, traumatic injury to spine, osteoporosis, and even obesity.

• The normal value for lumbar lordotic angle can be defined as 2-45 degrees with a range of 1 SD.
• Pregnant women are prone to developing a lumbar lordosis due to postural adjustments related to attempted posterior leaning to compensate for the increased weight in the front of the body, and to reduce pain from the stress on back extensor muscles working to keep the body upright when the body’s center of mass has shifted forward.

https://pubmed.ncbi.nlm.nih.gov/1354697/

https://www.spineuniverse.com/conditions/spinal-disorders/closer-look-lordosis

Scoliosis: Defined as a lateral or sideways curvature of the spine (>10%) with rotation of the vertebrae resulting in an abnormal C-shaped or S-shaped curve. Scoliosis is the most common spinal disorder in children and adolescents. Idiopathic scoliosis is classified into the following subgroups:

• Infantile Scoliosis: Develops at the age of 0-3 years and has a prevalence of 1%. A significant decrease in infantile scoliosis occurred in the 1980’s related to the recommendation of prone position for infants.
• Juvenile Scoliosis: Develops at the age of 4-10 years and compromises 10-15% of all idiopathic scoliosis in children.
• Adolescent Idiopathic Scoliosis (AIS): Develops at the age of 11-18 years and accounts for approximately 90% of cases of idiopathic scoliosis in children. Adolescent Idiopathic Scoliosis (AIS) is a common disease with a prevalence of 0.47 – 5.2%. Prevalence and curve severity are higher for girls than for boys, and the female to male ratio increases with increasing age of the children. However, statistical data is obtained by school screening which are known to have many limitations yielding a low overall positive predictive value for detecting curves. 97% of AIS patients are related to other family members with AIS.
• Gender and Severity of Curve: An overall prevalence ratio of 2:1 female to male exists with girls progressing to a higher degree of curvature compared to boys.
• Curve Type: Thoracic curves are most common (48%), followed by thoracolumbar/lumbar curves (40%). Double curves (9%).
• Curve Type According to Gender: Boys have a higher proportion of thoracolumbar/lumbar curves; girls have a higher prevalence of thoracic and double curves.
• Curve Type According to Age: In the infantile age rotation is predominantly to the left, in adolescent age it is to the right, and in juvenile age there is no predominant rotation to either side.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3566258/

Sacroiliac Joint (SIJ) Dysfunction: Sacroiliac joint dysfunction can result from various clinical conditions, abnormal motion or malalignment of the SI joint. It manifests as pain in localized to an area of approximately 3 cm x 10 cm that is inferior to the ipsilateral posterior superior iliac spine. Referred pain maps from SIJ dysfunction extend in the L5-S1 nerve distributions, commonly seen in the buttocks, groin, posterior thigh, and lower leg with radicular symptoms.

• The prevalence of SIJ dysfunction among patients with LBP is estimated to be 15% to 30%, this is a substantial number considering that about 74 million individuals in the US experience LBP in the last 3 months.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6707638/

Spinal & Foraminal Stenosis: Spinal stenosis is a narrowing of the spinal canal or the neural passageways (foramina) that can put pressure on the spinal cord or spinal nerve roots at any part of the spine.

• Approx. 250,000 – 500,000 in the United States have symptoms of spinal stenosis. This represents about 1 per 1,000 persons older than 65 years and about 5 of every 1,000 persons older than 50 years. https://www.medscape.com/answers/1913265-68823/what-is-the-prevalence-of-spinal-stenosis
• According to the AAOS, lumbar spinal stenosis affects 8 to 11 percent of the US population. https://onsmd.com/condition/spinal-fractures-spinal-stenosis/
• According to the Framingham Study, congenital lumbar spinal stenosis (LSS) was found in 4.7% and absolute LSS was found in 22.5% and in 7.3%, respectively. Acquired LSS showed increasing prevalence with age: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3775665/

Thoracic Outlet Syndrome (TOS): TOS constitutes a group of diverse disorders that result in compression of the neurovascular bundle (brachial plexus, subclavian artery, and subclavian vein) exiting the thoracic outlet. The thoracic outlet is an anatomical area in the lower neck defined as a group of three spaces between the clavicle and the first rib through which several important neurovascular structures pass. Compression of these neurovascular structures can cause a variety of symptoms including upper extremity pallor, paresthesia, muscle weakness and atrophy, and pain.

• Neurological TOS accounts for 95-99% of all neurologic cases, mostly affects the lower brachial plexus (80% disputed) with the other 20% (true) affecting the upper brachial plexus, and is more common in women. True neurological TOS is primarily unilateral, whereas disputed TOS is often bilateral.
• Venous TOS accounts for 3-5% of cases, tends to be unilateral, and is more common in men, especially younger men due to its association with repetitive upper extremity activity.
• Arterial TOS accounts for 1-2% of cases, is predominantly unilateral, and affects both genders equally.
• Cervical Rib: Approximately 1-2% of the population has a cervical rib, which is estimated to account for 20% of all neurological TOS cases.
• TOS Symptom Distribution: Upper extremity paresthesia (98%), neck pain (88%), trapezius pain (92%), shoulder and/or arm pain (88%), supraclavicular pain (76%), chest pain (72%), occipital headache (76%), paresthesias in all five fingers (58%), the fourth and fifth fingers only (26%).

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6514035/

The shoulder joint complex is comprised of the scapula and clavicle via its attachment to the manubrium of the sternum, and the humeral head articulating with the glenoid cavity of the scapula. Because of the high degree of mobility available at the shoulder joint complex and this can lead to a greater risk for injury to the shoulder muscular and support structures.

Acromioclavicular Joint Sprain/Separation: This is an injury where the clavicle separates from the acromion process of the scapula causing damage to the superior and inferior acromioclavicular ligaments and potentially the coracoclavicular ligament (conoid and trapezoid heads) that help stabilize the joint. There are two primary mechanisms of injury for an AC sprain: falling on the tip of the shoulder or falling on an outstretched arm/hand. AC injuries can be associated with fractured clavicle, impingement syndromes, and neurovascular insults.

• Accounts for more than 40% of all shoulder injuries among athletes and young individuals.
• Accounts for nearly 10% of all injuries in collision sports such as football, ice hockey, lacrosse, etc.
• The most frequently encountered complication of AC joint separation is residual joint pain affecting anywhere from 30% to 50% of individuals.

https://www.ncbi.nlm.nih.gov/books/NBK493188/

Adhesive Capsulitis (Frozen Shoulder Syndrome): This inflammatory shoulder joint capsule condition is characterized by shoulder pain, stiffness, and decreased range of motion, especially in external rotation and abduction. As an idiopathic condition (classified as a primary disease), it has an increased prevalence in patients with diabetes mellitus and hypothyroidism. As a secondary disease classification, it typically follows post trauma to the shoulder and is associated with immobilization of the extremity.

• Adhesive capsulitis has a prevalence of approximately 2% to 5% percent in the general population, with a mean age of onset at 55 years of age.
• Women develop the condition at a ratio of 1.4:1 over men.
• Usually, the non-dominant arm is affected.
• Long-term disability has been reported at 10% to 20% in patients, and persistence of symptoms in 30% to 60%.

https://www.ncbi.nlm.nih.gov/books/NBK532955/

Bicipital Tendonitis (Long Head Biceps): A painful and inflammatory clinical condition of tenosynovitis affecting the tendon and synovium of the long head of the biceps brachii muscle that originates from the supraglenoid tubercle and supraglenoid labrum of the scapula and runs through the bicipital groove on the anterior surface of the upper humeral bone between the greater and lesser tubercles. This condition can worsen and become acute inflammatory tendinitis and degenerative tendinopathy.

• Primary LHB tendinitis represents approx. 5% of cases of proximal biceps pathology and are typically observed in younger athletes participating in baseball, softball, volleyball, gymnastics, and swimming.
• LHB tendinopathy often occurs in association with RC, EI/SIS, or in tandem with subscapularis injuries. In the setting of RC tears, 90% of cases demonstrated concomitant LHB tendinopathy, and 45% of cases had additional LHB instability.

https://www.ncbi.nlm.nih.gov/books/NBK533002/

Fractured Clavicle: The clavicle or collar bone articulates with the manubrium medially (sternoclavicular joint) and the acromion process (acromioclavicular joint) of the scapular laterally and is involved in scapular movements. A fracture to the clavicle is most commonly caused by falling onto the lateral shoulder (87% or reported cases).

• A fractured clavicle affects 1 in 1,000 people per year with two-thirds occurring in males in a bimodal distribution (1 peak among men younger than 25 - sports related, and the other peak in those older than 55 years of age – falls).
• Fractures to the clavicle accounts for 2% to 10% of all fractures and is the most common fracture in childhood.
• Approx. 20% of females and more than 33% of males with clavicular fractures are between 13-20 years old.
• The middle third of the clavicle represents 95% of fractures seen in children. In children younger than 10 most are non-displaced, while in children older than 10 most are displaced.
• Clavicular fractures represent 95% of fractures seen in childbirth.

https://www.ncbi.nlm.nih.gov/books/NBK507892/

Glenoid Labrum - Bankart Lesion: Defined as a lesion to the anterior part of the glenoid labrum of the shoulder often caused by acute or repeated anterior shoulder dislocation.

• In arthroscopic Bankart repair, the muscle strength is regained faster, but the recurrence rates after open Bankart repair are significantly lower. In addition, the recurrence rate after operative Bankart treatment is significantly reduced compared to a non-operative treatment with recurrent instability rates ranging from 17% to 96% in patients under age of 30 years.

https://www.physio-pedia.com/Bankart_lesion

Glenoid Labrum - SLAP Tear: The labrum is a cartilage structure that surrounds the glenoid fossa of the shoulder joint. Its purpose is to deepen the socket and provide an attachment for the shoulder joint capsule. The term SLAP lesion or tear stands for Superior Labrum Anterior to Posterior indicating the position and directional elements of the labrum tear (10 o’clock to 2 o’clock).

• A landmark study evaluating trends in SLAP repair found SLAP tears were more common in men (>3:1) compared to women.
• The highest incidences of SLAP repairs were found in the 20 to 29 and 40 to 49 decades at 29.1 and 27.8 per 10,000 patients, respectively.
• Repetitive overhead athletes, baseball pictures, tennis players, and manual laborers have an increased risk for SLAP tears, and acutely, traumatic injury can occur in traction/torsion and compressive/subluxation mechanisms. Consequently, there are several proposed mechanisms for the cause of SLAP tears – a fall on an extended and abducted arm, the cocking phase of throwing, a biceps tendon implication during the eccentric contraction of throwing follow through, etc.

https://www.ncbi.nlm.nih.gov/books/NBK557662/

Hill-Sachs Lesion: A compression fracture or “dent” of the posterosuperolateral humeral head that occurs in association with anterior instability or dislocation of the glenohumeral joint.

• This lesion occurs in approx. 50% of first-time anterior shoulder dislocations, and for people with chronic shoulder dislocation history it is present in most cases.

https://www.physio-pedia.com/Hill_Sachs_Lesion

Rotator Cuff Injury: The rotator cuff consists of four muscles that originate on the scapula and insert on the two humeral tubercles (subscapularis on the lesser tubercle, and the supraspinatus, infraspinatus, and teres minor on the greater tubercle). These four muscles serve to 1) stabilize the humeral head in the glenoid fossa, 2) initiation rotary movements at the shoulder joint, and 3) decelerate rotary movements at the shoulder joint. Rotator cuff injury includes tendonitis, tendinopathy, impingement, partial tears, and complete tears.

• Rotator cuff injury is the most common tendon injury seen and treated.
• Age is the most common factor for rotator cuff disease, with approximately 30% of adults over 60 have a tear, and 62% of adults over 80 have tears.
• Leading risk factors for rotator cuff disease is smoking, family history, and poor posture. Rotator cuff tears were present in 65.8% of patients with kyphotic-lordotic postures, 54.3% with flat-back postures, and 48.9% with sway-back postures; tears were present in only 2.9% of patients with ideal postural alignment.
• Rotator cuff starts from trauma (repetitive, overhead activities) with acute tears generally seen in younger patients and tendon degeneration tears seen in older patients.
• Specific to tears, actively enlarging tears have a five times higher likelihood of developing symptoms than those that remain the same size, and anterior tears are more likely to progress cuff degeneration.

https://www.ncbi.nlm.nih.gov/books/NBK547664/

Shoulder Arthroplasty: Total shoulder arthroplasty involves the surgical removal of portions of the shoulder joint, which are replaced with artificial implants to reduce pain and restore range of motion and mobility. This procedure is considered the best intervention for shoulders with osteoarthritis and inflammatory arthroplasty. There is a range of options including resurfacing of the humeral head, anatomic hemiarthroplasty, total shoulder arthroplasty, and reverse shoulder arthroplasty.

• The primary reasons for total shoulder arthroplasty are advanced glenohumeral arthritis, rotator cuff arthropathy, and proximal humerus fractures.
• Pain is improved in over 90% of individuals suffering from primary osteoarthritis, and 80% in those suffering from osteonecrosis who receive shoulder arthroplasty.
• Between 2011 and 2017, the number of primary shoulder arthroplasties increased by 103.7%. Reverse shoulder arthroplasties increased 191.3%.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3093753/

Shoulder Dislocation: The shoulder joint is relatively unstable due to its shallower socket (as compared to the hip joint) and shoulder dislocations represent 50% of all major joint dislocations. While the shoulder can dislocate anteriorly, posteriorly, and inferiorly, anterior dislocation is the most common.

Anterior shoulder dislocations account for 97% of all shoulder dislocations.

• The most common mechanism of injury is a blow/force to a shoulder that is abducted, externally rotated, and horizontally abducted.
• There are associated injuries in up to 40% of anterior dislocations including nerve, tears to the glenoid labrum, and fractures to the glenoid fossa, and/or humeral head.
• On exam, the arm will be held in an abducted and externally rotated position.

Posterior shoulder dislocations account for 2% to 4% of shoulder dislocations.

• The most common mechanism of injury is a hit to the anterior shoulder and axial loading of an adducted and internally rotated shoulder.
• Poses a higher risk for associated injuries – surgical neck fractures, reverse Hill-Sachs lesions, and injuries to the labrum and rotator cuff.
• On exam, the arm will be held in an adducted and internally rotated position.

Inferior shoulder dislocations account for less than 1% of dislocates.

• Usually caused by hyperabduction or with axial loading on an abducted arm.
• On exam, the arm is held above and behind the head and the patient is unable to adduct arm.
• Often associated with nerve injury, rotator cuff injury, tears in the internal capsule, and the highest incidence of axillary nerve and artery injury of all shoulder injuries.

https://www.ncbi.nlm.nih.gov/books/NBK459125/

Shoulder Impingement Syndrome: Shoulder impingement syndrome is where soft tissues, primarily the supraspinatus muscle or long head of the biceps muscle, become impinged between the head of the humerus and the acromion process of the scapula, known as the subacromial space. Impingement is associated with a narrowing of the subacromial space with pain being manifest with elevating the arm, a forced overhead movement, or when lying on the affected side.

• Shoulder impingement was first described in 1852 and is believed to be the most common cause of shoulder pain, accounting for 44% to 65% of all shoulder complaints.
• Shoulder impingement syndrome is most commonly seen in individuals who participate in sports or activities that require overhead activities, including handball, volleyball, swimming, carpentry work, painters, and hairdressers.
• Other factors that may predispose a person to develop impingement are infection, smoking, and fluoroquinolone antibiotics.
• The peak incidence of shoulder impingement syndrome occurs in the sixth decade of life.
• In 60% of patients, therapeutic interventions typically yield satisfactory results within two years.

https://www.ncbi.nlm.nih.gov/books/NBK554518/

Sternoclavicular (SC) Joint Sprain or Dislocation: The sternoclavicular joint is a complex saddle joint located between the manubrium of the sternum and the sternal end of the clavicle. Along with the acromioclavicular joint, the SC joint work together in the movements of the scapula over the thoracic ribcage.

• Traumatic sternoclavicular injuries are rate and account for less than 3% of all traumatic joint injuries. Dislocations of the SC joint comprise 1% of all joint dislocations, and 3% of those in the upper limb, with young active males have the greatest prevalence of SC joint injuries.
• Traumatic posterior SC joint dislocations can damage and compromise the subclavian vein, the internal jugular vein, the internal thoracic artery, the subclavian artery, the brachiocephalic vessels, the trachea, the esophagus, and the phrenic and vagus nerves. These injuries can result in swelling and cyanosis of the arm, cervical bruit, respiratory distress, stridor, tracheal hematoma, diaphragmatic paralysis and death.
• In a systemic review, Glass et al (https://pubmed.ncbi.nlm.nih.gov/21610444/) identified 251 SC dislocations in which 117 patients had anterior dislocations. They found excellent to good results were achieved in the non-operative group in 69% of patients with anterior dislocations. Patients with acute dislocations managed with closed reduction fared better than patients treated solely by surgical treatment (92% vs 76% excellent/good results).
• In children, approximately 40% to 50% of all posterior fracture dislocations are physeal separations.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6134883/

Subacromial Bursitis: The subacromial bursa is a fluid-filled sac located under the acromion process of the scapula that lubricates the structures of the subacromial space against friction – bordered superiorly by the acromion, coracoid, and coracoacromial ligament and the proximal deltoid muscle fibers and inferiorly by the supraspinatus muscle. Subacromial bursitis is an inflammatory condition that is a common cause of shoulder pain. It is typically caused by repetitive overhead activities and minor trauma.

• Bursitis accounts for approximately 0.4% of all primary care visits.
• Gender prevalence is equal and more often seen in individuals who participate in repetitive overhead activities – athletes (throwers, racket sports, swimmers) factory workers, and manual labors.

https://www.ncbi.nlm.nih.gov/books/NBK541096/

Cubital Tunnel Syndrome (Ulnar Nerve Entrapment): The cubital tunnel is the space between the medial epicondyle of the humerus bone and the olecranon of the ulna bone and covered by the cubital tunnel retinaculum, a strong connective tissue sheath. The ulnar nerve runs through the tunnel and is often referred to as the “funny bone”. Because the ulnar nerve follows a relatively constrained path, flexion of the elbow causes the nerve to both slide and stretch (up to 5mm) through the cubital tunnel. Further, the further the elbow goes into flexion the shape of the tunnel changes from an oval to an ellipse, effectively narrowing the canal by 55% and increasing the intraneural pressure by up to six times. The result is pain, tingling, and numbness in the hand along the ulnar dermatomal pattern – ring and little finger.

• Cubital tunnel syndrome is the second most common peripheral nerve entrapment syndrome in the human body.
• As with all nerve disorders, patients with diabetes mellitus are at increased risk of ulnar nerve symptoms. Other risk factors are protracted periods of elbow flexion (e.g., holding telephones), repetitive elbow flexion/extension movements (throwers), operation of vibrating tools, direct blow to the area (funny bone), and obesity.
• The estimated incidence rate ratio of cubital tunnel syndrome is 0.08 to 8.0 cases per 1,000 person-years.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2599973/

https://pubmed.ncbi.nlm.nih.gov/30266478/

Elbow Dislocation: The elbow is the articulation between the distal humerus and the proximal ulna and radius and is among the most common large joints to dislocate. In children, it is the most common large joint dislocation, and is often accompanied by medial epicondyle fractures. The classification of elbow dislocations is based on the direction of the dislocation: posterior, posterolateral, posteromedial, lateral, medial, or divergent. Elbow dislocation is also classified as simple, without associated fracture, or complex, with associated fracture.

• The radial head is usually fractured in adults with a complex elbow dislocation.
• Falling onto an outstretched hand is he most common mechanism leading to elbow dislocations.
• The incidence of elbow dislocations is 5.21 per 100,000 person years.
• Elbow dislocations are more common in males than females, 53% versus 47%, respectively.
• Males have nearly double the incidence of dislocations in the second decade of life and accounts for nearly half (43.5%) of the elbow dislocations.
• Over half of dislocations occur at home, followed by at work and at school.
• The sport with the highest rate of elbow dislocations is football, followed by roller-blading, skate boarding, and wrestling.
• Loss of elbow range of motion is the most common complication with a greater loss occurring in extension ROM.

https://www.ncbi.nlm.nih.gov/books/NBK549817/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6447645/

Lateral (Radial) Collateral Ligament Injury of the Elbow: The elbow joint complex derives its stability from both bony configuration and soft-tissue constraints. The medial collateral ligament is the main static stabilizer of the elbow against valgus and internal rotation stress. The lateral collateral ligament resists excessive varus and external rotation stress.

• Posterolateral rotary instability (PLRI) is the most common form of chronic elbow instability and is usually the result of a fall on the outstretched hand that upon impact, causes the radial head and ulna to rotate externally leading to a posterior displacement of the radial head causing disruption of the elbow lateral stabilizers.
• Conservative treatment for PLRI is usually ineffective. Reconstructive surgery leads to good to excellent outcomes, but recurrence can be seen in up to 25% of patients.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5367576/

Lateral Epicondylitis: Defined as inflammation of the tendons of the wrist extensor muscles as they originate from the lateral epicondyle of the elbow (also known as tennis elbow).

• It affects between 1% and 3% of the population, generally affecting the middle-aged without gender predisposition.
• Most cases of lateral epicondylitis are self-limiting with 90% of patients recovering within 1 year.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5367546/

Medial (Ulnar) Collateral Ligament Injury of the Elbow: The elbow joint complex derives its stability from both bony configuration and soft-tissue constraints. The medial collateral ligament is the main static stabilizer of the elbow against valgus and internal rotation stress. The lateral collateral ligament resists excessive varus and external rotation stress. Elbow medial collateral ligament sprain occurs when the elbow is subjected to a valgus force exceeding the tensile properties of the medial collateral ligament (MCL). This is an injury seen more often in throwing athletes.

• Patients with MCL injuries complain of medial elbow pain during the acceleration phase of throwing. Chronic injuries present gradually and often with pain occurring only when throwing 50–75% of maximal effort. Acute injuries may present suddenly with a pop, sharp pain, and inability to continue throwing.
• Jobe developed the original MCL reconstruction, dubbed the “Tommy John Procedure” in 1974.
• The average rate of UCL surgeries in the 155 Division I collegiate baseball programs enrolled for the 2016-2017 year was 0.86 per program. The risk of a surgical injury was much higher for pitchers, as 4.4% of all pitchers underwent UCL surgery during the 1-year period. Pitchers who were underclassmen were at an increased risk of an injury requiring surgery. Awareness of these factors should be considered in injury prevention.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5900821/

Medial Epicondylitis: Defined as inflammation of the tendons of the wrist flexor muscles as they originate from the medial epicondyle of the elbow (also known as Little League or pitcher’s elbow, and golfer’s elbow). It is primarily caused by a repetitive strain from activities that involve frequent loaded gripping, forearm pronation, and/or wrist flexion.

• Commonly seen in throwing athletes, golfers, bowlers, rock climbers, archers, weightlifters and those that use tools that require gripping and repetitive movements.
• Is much less common that lateral epicondylitis, making up only 10% of all cases of epicondylitis.
• Affects females more than males and is more common in middle-aged individuals.
• Most cases of medial epicondylitis are self-limiting with 80% of patients recovering within 1 to 3 years.

https://www.ncbi.nlm.nih.gov/books/NBK557869/

Nurse Maid’s Elbow: Nurse Maid’s Elbow is a radial head subluxation injury that is common in young children where the radial head slips out from under the annual ligament causing pain and an inability to supinate the forearm. The mechanism of injury is an axial traction of a pronated forearm and extended elbow.

• Most common in children 1-4 years of age.
• Represents more than 20% of upper extremity injuries in children, with a slight female predominance and a slight left arm predominance. Recurrence rate is 20%.

https://www.ncbi.nlm.nih.gov/books/NBK430777/

Olecranon Bursitis: Olecranon bursitis is a condition where the fluid filled subcutaneous bursal sac, superficial to the olecranon process, becomes inflamed. It can be an acute condition caused by direct trauma, or a chronic condition mostly caused by pressure or compression, such as leaning on elbows for an extended period.

• The most common population affected is men between the ages of 30 and 60 years.
• Two-thirds of cases are non-septic and occur from repeated trauma to the elbow.

https://www.ncbi.nlm.nih.gov/books/NBK554617/

https://www.ncbi.nlm.nih.gov/books/NBK470291/

Radial Nerve Entrapment: Radial nerve entrapment is a condition, usually caused by overuse, in which the radial nerve becomes compressed or entrapped, with the most frequent location of entrapment occurring in the forearm in the proximity of the supinator muscle and often involves the posterior interosseous nerve branch. Pain and altered sensation is experienced in the radial nerve distribution distal to the point of compression.

• The annual incidence rate of posterior interosseous nerve compression is estimated to be 0.03%, while the rate for superficial radial nerve compression is estimated to be 0.003%.

https://www.ncbi.nlm.nih.gov/books/NBK431097/

Carpal Tunnel Syndrome: Carpal tunnel syndrome is a condition in which the median nerve becomes pressed as it passes through the carpal tunnel (along with 9 tendons from three muscles) formed by the carpal bones of the wrist and the transverse carpal ligament that covers the carpal tunnel. The median nerve innervates the forearm flexor muscles and five intrinsic hand muscles, and the sensory fibers innervate the skin on the palmar surface of the hand and the thumb, index, and middle finger. If the nerve is pressed, it can result in pain, tingling, numbness in the skin previously described.

• Women are three times more likely than men to develop carpal tunnel syndrome, and people with diabetes and other metabolic disorders that affect the nerves are at greater risk.
• Carpal Tunnel Syndrome is the most common nerve entrapment neuropathy, accounting for 90% of all neuropathies.
• In the United States, carpal tunnel syndrome (CTS) has an incidence of 1 to 3 persons per 1000 per year, with a prevalence of 50 per 1000, with similar incidence and prevalence in most developed countries.
• It most commonly affects Whites. Whites are two to three times more prone to get affected than Blacks.
• The peak age of CTS occurrence is 40-60 years.
• CTS is ten times more common in females as compared to males

https://www.ncbi.nlm.nih.gov/books/NBK448179/

De Quervain’s Tenosynovitis: This is a repetitive overuse problem that produces a thickening of the tendon sheaths and entrapment of the abductor pollicis longus and extensor pollicis brevis muscles as their tendons through the fibro-osseous tunnel of the extensor retinaculum which covers the first dorsal compartment located along the radial styloid. The pain of this condition is accentuated when the person flexes their thumb and tucks it under the index finger and then performs wrist ulnar deviation.

• The estimated prevalence of de Quervain tenosynovitis is about 0.5% in men and 1.3% in women with peak prevalence among those in their forties and fifties.
• The highest incidence de Quervain’s is found in black and white women.
• Diabetes, rheumatoid arthritis, lupus, and hypothyroidism are associated with an increased risk.
• It is commonly seen in individuals with a history of medial or lateral epicondylitis and appears prevalent in new mothers and childcare providers from repeated lifting of the child.

https://www.ncbi.nlm.nih.gov/books/NBK442005/

Distal Radius Fracture (Colles Fracture): Defined as a distal radius fracture with dorsal comminution, displacement, and dorsal shortening, often with an associated fracture of the ulnar styloid. The mechanism of injury for a Colles fracture is falling on an outstretched hand with the wrist in extension or dorsiflexion.

• Colles Fracture primarily affects two main populations; young athletes (often around the time of puberty when bone mineralization is low) and the elderly (associated with falls and osteoporosis – why women are more likely to sustain this injury), and is the most common fracture of the distal radius in adults. The age group of 19 to 49 years makes up the least common age group for this injury.
• In the United States, there is an incidence of around 67 upper extremity fractures per 10,000 people annually. Distal radial and ulnar fractures account for approximately 25% of these fractures.

https://www.ncbi.nlm.nih.gov/books/NBK553071/

https://www.ncbi.nlm.nih.gov/books/NBK536916/

Distal Radius Fracture (Smith’s Fracture): Defined as a distal radius fracture with volar displacement or angulation, typically resulting from a fall on the dorsum of the hand with the wrist flexed.

• As one of the “distal radius fractures, they are the second (to hip fractures) most common fracture in the elderly.
• Smith fractures make up approximately 5% of all radial and ulnar fractures combined. The highest incidence of Smith's fractures is in young males and elderly females. Almost all distal radius fractures arise in children sustaining high-energy falls and osteoporotic seniors who suffer low-energy falls.
• Women are six times more likely than men to sustain this type of fracture.

https://www.ncbi.nlm.nih.gov/books/NBK547714/

Dupuytren’s Contracture: Dupuytren’s is a chronic progressive fibroproliferative hand disorder that produces hard nodules in the palmar aponeurosis, leading to the formation of longitudinal fibrous bands, resulting in flexion contractures of the metacarpophalangeal (MCP) and/or proximal interphalangeal (IP) joints. This condition is believed to be linked to hereditary and its risk of development is increased by smoking, alcoholism, diabetes, nutritional deficiencies, or certain medications.

• This condition is most commonly seen in populations of Northern European/Scandinavian descent.
• The most commonly affected digits are the fourth (ring) and fifth (little) fingers.
• Dupuytren contracture is usually seen in whites and the disorder is often bilateral; when unilateral, the right side is more likely to be involved compared to the left.
• Ectopic manifestations beyond the hand can be seen in Ledderhose disease (plantar fascia), 10% to 30%; Peyronie disease (Dartos fascia of the penis), 2% to 8%; and Garrod disease (dorsal knuckle pads), 40% to 50%.
• The disorder is not always progressive and in at least 50-70% of patients, it may stabilize or even regress.

https://www.ncbi.nlm.nih.gov/books/NBK526074/

Finger Dislocation: Finger dislocation is a common hand injury and can occur at the proximal interphalangeal (PIP), distal interphalangeal (DIP), or metacarpophalangeal (MCP) joints. Both the PIP and DIP joints are ginglymus joints allowing normal movement in the sagittal plane of motion, and the MCP is a condyloidal joint allowing normal movement in both the sagittal and frontal planes of motion.

• The most common MCP joint dislocation is the index finger. MCP joint dislocation of the middle finger occurs more frequently when it is subjected to ulnar stress while in hyperextension. Most common MCP joints dislocate dorsally. MCP joint dislocations have the high likely hood of requiring operative intervention, and recovery to preinjury motion takes approximately 4 to 6 weeks.
• PIP joint dislocations are the most common dislocation due to sports. PIP joint dislocation is most commonly dorsal; however, volar dislocation correlates with a higher rate of complications and more difficult reductions. Most PIP joint dislocations are stable after reduction except lateral PIP joint dislocation as they often require surgical intervention.
• DIP joint dislocations typically present with deformity at the fingertip and most frequently occur dorsally with associated fractures and skin injuries. Isolated DIP joint dislocation is rare, and like PIP joint dislocation, lateral DIP joint dislocation more often requires surgical intervention.
• From 2004 to 2008, approximately 166000 finger dislocations received treatment in US Emergency Departments. Most dislocations occur between fifteen and nineteen years of age and affect African Americans more than other racial groups. They occur most commonly in basketball and football players.

https://www.ncbi.nlm.nih.gov/books/NBK551508/

Ganglion Cyst: A ganglion cyst is a fluid-filled, noncancerous lump that rises out of the tissues surrounding a joint. While they occur in various locations, they most frequently develop on the back of the wrist and their origin is considered idiopathic. However, a cyst is believed to arise from repetitive microtrauma resulting in mucinous degeneration of connective tissue.

• Ganglion cysts account for 60% to 70% of soft-tissue masses found in the hand and wrist.
• Ganglion cysts are most commonly found (70%) on the dorsal aspect of the wrist arising from the scapholunate ligament or scapholunate articulation. Approximately 20% of ganglion cysts are located on the volar aspect of the wrist arising from the radiocarpal joint or scaphotrapezial joint. The remaining 10% of ganglion cysts can arise from multiple areas of the body including the volar retinaculum of the wrist, distal interphalangeal joint, ankle joint, and foot. 
• Ganglion cysts are most commonly found in women between the ages of 20 to 50. Women are three times more likely to develop a ganglion cyst than men.

https://www.ncbi.nlm.nih.gov/books/NBK470168/

Guyon’s Canal Syndrome: Guyon’s Canal Syndrome is a peripheral ulnar neuropathy as the ulnar nerve passes through a narrow anatomic corridor called Guyon’s Canal at the wrist, formed between the pisiform carpal bone and the hamulus of the hamate carpal bone, with the volar carpal ligament as the roof and the transverse carpal ligament as the floor. Because of its location, this nerve is vulnerable to compressive forces.

• Some studies estimate that 30% to 40% of Guyon canal syndromes result from ganglion cysts, with repetitive trauma being the second most common cause. Another study estimates 45% of cases to be idiopathic.
• The incidence and prevalence of Guyon canal syndrome in the general population have not yet been accurately estimated due to the lack of studies.

https://www.ncbi.nlm.nih.gov/books/NBK431063/

Mallet Finger: Mallet finger involves the rupture of the extensor digitorum tendon at its insertion on the dorsal surface of the distal phalanx of the finger, resulting in a flexion deformity of the distal finger joint. The most common mechanism is a sudden flexion of the DIP joint with resistance force directed along the long axis of the finger. If left untreated, mallet finger leads to a swan neck deformity from PIP joint hyper extension and DIP joint flexion. Most mallet finger injuries can be managed non-surgically, but occasionally surgery is recommended for either an acute or a chronic mallet finger or for salvage of failed prior treatment.

• Splinting is the most common initial treatment method for soft tissue or bony mallet finger. Bony mallet fingers with more than 30 % articular involvement with joint subluxation are better managed surgically.
• Mallet finger injuries are most commonly seen in young and middle aged male patients. The mean age for males is 34 compared with 41 in females.
• 74% of bony mallet finger injuries involves the dominant hand, and more than 90 % of injuries was found in the ulnar 3 digits 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4022957/

Scaphoid Fracture: The scaphoid is the first carpal bone on the radial side of the first or proximal row of carpal bones of the wrist. It is the primary carpal bone that articulates with the distal radius making the wrist joint. The typical mechanism of injury is falling on an outstretched hand or an axial loading of the wrist with it in forced hypertension and radial deviation.

• Scaphoid fractures predominantly affect young adults, with a mean age of 29 years, and a higher incidence in males. This type of fracture is unusual in the pediatric and elderly populations, where the physis or distal radius, are more likely to fracture first.
• Scaphoid fractures account for 15% of acute wrist injuries, 2% to 7% of all fractures, and 60% to 70% of carpal bone fractures.
• Misdiagnosis can lead to increased morbidity for the patient, as the risks of non-union can be high (14% to 50%). If left untreated, arthritis, deformity, and instability invariably develop within five years, leading to a significant disability.

https://www.ncbi.nlm.nih.gov/books/NBK536907/

Skier’s Thumb (Gamekeepers Thumb): Skier’s thumb is a partial or complete rupture of the ulnar collateral ligament of the metacarpophalangeal joint of the thumb, and has a serious risk of disabling chronic instability if not treated adequately.

• The estimated incidence in the United States is approximately 200,000 patients per year. It is related to 86% of all injuries to the base of the thumb.
• Most UCL injuries occur at the distal attachment on the proximal phalanx, and associated bony avulsion fractures are seen in 20% to 30% of UCL ruptures.

https://www.ncbi.nlm.nih.gov/books/NBK499971/

Trigger Finger: Trigger finger is caused by inflammation and subsequent narrowing of the A1 pulley flexor sheaths combined with hypertrophy and inflammation of the tendon/sheath interface, which causes pain, clicking, catching, and loss of motion of the affected finger. This produces a locking of the digits during either flexion or extension. Trigger finger commonly affects the dominant hand and the most common digit involved is the thumb. 

• Trigger finger has a bimodal incidence, with a first peak before eight years of age and the second peak in patients in their 40s and 50s.
• Overall, trigger finger is more common in adults. When children get trigger finger, it affects boys and girls equally and is most common in the thumb. In adults, women are much more likely to be affected by trigger finger, and typically, in their dominant hand.
• In adult trigger finger, there can be an association with the diseases of diabetes, amyloidosis, carpal tunnel syndrome, gout, thyroid disease, and rheumatoid arthritis.

https://www.ncbi.nlm.nih.gov/books/NBK459310/

Avascular Necrosis (AVN): Avascular necrosis of the femoral head is a type of osteonecrosis due to disruption of the blood supply to the proximal femur, the majority of which is provided by the medial and lateral circumflex branches of the profunda femoris branch of the femoral artery. The pathology can occur due to a variety of causes, either traumatic or atraumatic. Leading causes include femoral neck fractures, hip dislocation, chronic steroid use, sickle cell disease, systemic lupus erythematosus, chronic alcohol consumption, coagulopathy, and congenital causes. The outcome of this disease can result in death of osteocytes and bone marrow ultimately resulting in collapse of the femoral head and subsequent osteoarthritis.

• There are approximately 10,000 to 20,000 new cases reported each year in the United States, contributing to 10% of the approximately 250,000 total hip arthroplasties performed annually.
• AVN is more prevalent in men than women, with ratios estimated to be between 3:1 to 5:1.
• The average age at treatment is 33 to 38 years old.

https://www.ncbi.nlm.nih.gov/books/NBK546658/

Femoroacetabular Impingement (FAI): An anatomical morphologic abnormality condition (Cam deformity – aspherical morphology of the proximal femur, Pincer deformity – general overcoverage of the femoral head by the acetabulum, and Mixed – a combination of both) where the proximal femur impinges on the acetabulum causing hip pain. Overtime this can lead to cartilage wear and tear of labrum and eventually hip osteoarthritis.

• Using a cut-off of MRI measured alpha angle of > 50.5° for defining the presence of a cam deformity, Hack et al. studied a cohort of 400 hips from 200 of asymptomatic adults without a history of childhood hip disease (mean age 29.4 years, 79 % white, 55.5 % women) (7) and reported a prevalence of cam deformity of 14%, of which 79 % were men. In a study of 3,620 adults (mean age 60 years, predominantly white, 63.2 % women) without a history of childhood hip disease, Gosvig et al. reported a prevalence of 19.6 % and 5.2 % for cam deformity in men and women respectively.
• The epidemiology of symptomatic FAI was recently evaluated in a cross-sectional study of 1076 subjects from clinical practices in the United States that underwent surgery. The authors reported that 55% of the population were female, average age of 28 years, 47.6% had cam type impingement, 44.5% had combined cam/pincer, and 7.9% had pincer deformity.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4280287/

Femoral Neck Anteversion (FNA): FNA is the angle between the femoral neck and femoral shaft, indicating the degree of torsion of the femur. Differences in FNA affect the biomechanics of the hip, through alterations in factors such as moment arm lengths and joint loading.

• FNA varies by up to 30° within apparently healthy adults. 
• FNA goes through substantial development during growth with a change from 0° in early gestation to 30° at birth, decreasing to 15° in adulthood. 
• Normative data for FNA in the healthy adult population is highly dependent on the landmarks identified and imaging technique used, with mean values in the range of 7°–24°.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7542196/

Hamstring Strain: The hamstring muscle group comprises the lateral positioned biceps femoris and the medial positioned semitendinosus and semimembranosus muscles. This group of muscles is highly susceptible to injury due to 1) their anatomic arrangement over two joints that together with opposing effects on the hamstring length, 2) the role to decelerate the leg while walking, running, and making acute changes in direction at high speed (during the phase of motion when they transition from decelerating the extension of the knee to concentrically extending the hip joint), and 3) the biceps femoris has dual nerve supply to the two heads and the possibility of asynchronous stimulation.

• Hamstring injury peaks at 16 to 25 years of age and are the most common muscle injury in sports.
• It is mostly related to sports where hamstrings bear the most burden, with a rapid transition of its functional biomechanics at high speed like sprinting, soccer, football, track and field sports.
• One NFL study done over 10 years showed more than 50% injury during the preseason with mostly in positions like defensive secondary and wide receivers that demand more speed.
• Ethnicity, particularly African and Aboriginal origin have been found to associated with a higher incidence of hamstring injury as has having a previous hamstring injury.
• Sports that require rapid acceleration and deceleration like American football, soccer (accounting for 37% of muscle injuries), Australian rule football had more incidence of a hamstring injury. 
• Injury incidence is estimated at 3–4.1/1000 h of competition and 0.4–0.5/1000 h of training. 
• Of all muscle injuries, those of HS have one of the highest recurrence rates, which is estimated to range between 12% and 33%.

https://www.ncbi.nlm.nih.gov/books/NBK558936/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5582808/

Hip Fracture: A hip fracture is a break in the upper portion of the femur bone.

• Each year over 300,000 older people—those 65 and older—are hospitalized for hip fractures.
• More than 95% of hip fractures are caused by falling, usually by falling sideways.
• Women experience three-quarters of all hip fractures.
• Women fall more often than men.
• Women more often have osteoporosis, a disease that weakens bones and makes them more likely to break.

• Global hip fracture statistics were reported as 1.3 million in 1990, and depending on secular trends could be 7-21 million by 2050.
• Mortality associated with a hip fracture is about 5-10% after one month. One year after fracture about a third of patients will have died, compared with an expected annual mortality of about 10% in this age group. Thus, only a third of deaths are directly attributable to the hip fracture itself, but patients and relatives often think that the fracture has played a crucial part in the final illness. More than 10% of survivors will be unable to return to their previous residence. Most of the remainder will have some residual pain or disability.

https://www.cdc.gov/falls/hip-fractures.html

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1488757/

Hip Labral Tears: The etiology of hip labral tears includes trauma, femoroacetabular impingement, capsular laxity/hip hypermobility, dysplasia, and degeneration. Labral tears present with anterior hip or groin pain, and less commonly buttock pain.

• Across studies, tears were reported in all the regions of the labrum, and occasionally tears occurred in multiple regions in the same hip. Most tears reported in the United States occurred in the anterior portion of the labrum.
• Historically, labral tears were associated with slipped capital epiphyses, Legg-Calve-Perthes disease, major structural abnormalities of the hip, or high-velocity trauma, such as motor vehicle accidents or falls. It is now proposed that there are at least five etiologies of labral tears—trauma, FAI, capsular laxity/hip hypermobility, dysplasia, and degeneration.
• Degeneration is the final described etiology of labral tears. It has been suggested that these tears may represent the natural history of the aged joint, as labral abnormalities have been found in patients without hip pain with the incidence increasing with age. In cadaver studies, labral tears and abnormalities were found in 93–96% of hips.
• The most common associated lesions with labral tears in athletes are chondral injuries, which are usually adjacent to the labral pathology.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2697339/

Legg-Calve Perthes Disease: This condition is an idiopathic avascular necrosis of the capital femoral epiphysis of the femoral head that affects pediatric populations, and progresses through four stages. They are: 1) Initial Necrosis due to blood supply disruption, 2) Fragmentation as the body resorbs the necrotic bone and replaces it with weak woven bone, 3) Reossification and with stronger bone development, and 4) Healed/Remodeling when the bone growth is complete. After the completion of the four stages, there can still be deformity and limited range of motion.

• LCPD may be idiopathic or due to other etiology that would disrupt blood flow to the femoral epiphysis, such as trauma (macro or repetitive microtrauma), coagulopathy, and steroid use. Thrombophilia is present in approximately 50% of patients, and some form of coagulopathy is present in up to 75%.
• LCPD usually occurs between the ages of 3 to 12 years old, with the highest rate of occurrence at 5 to 7 years. It affects 1 in 1200 children under the age of 15.
• LCPD occurs most commonly in male patients, with a male to female ratio between 4:1 and 5:1. It is bilateral in 10% to 20% of affected cases.
• Usually a younger age at diagnosis equals a better outcome.

https://www.ncbi.nlm.nih.gov/books/NBK513230/

Piriformis Syndrome: Piriformis Syndrome is the compression of the sciatic nerve as it emerges from the greater sciatic notch by the piriformis muscle that crosses over the sciatic notch. The compressive force causes symptoms that are frequently described as pain that can tingling, burning, shooting, or aching in the center of the buttocks and along the course of the nerve down the posterior leg. Causes of piriformis syndrome include trauma to the buttocks area, piriformis hypertrophy, sitting for long periods of time, and anatomic abnormalities.

• Early division of the sciatic nerve into its tibial and common peroneal components can predispose patients to piriformis syndrome, with these branches passing through and below the piriformis muscle or above and below the muscle.
• Piriformis syndrome may be responsible for 0.3% to 6% of all cases of low back pain and/or sciatica.
• The incidence of piriformis syndrome is thought be roughly 2.4 million new cases per year.
• In the majority of cases, piriformis syndrome occurs in middle-aged patients with a reported ratio of male to female patients being affected 1:6.

https://www.ncbi.nlm.nih.gov/books/NBK448172/

Total Hip Arthroplasty (THA): Total hip replacement where the damaged bone and cartilage is removed and replaced with prosthetic components. The damaged femoral head is removed and replaced with a metal stem that is placed into the femur and a metal or ceramic ball is placed on the upper part of the stem to replace the head. The damaged cartilage surface of the socket is removed and replaced with a metal socket and a plastic, ceramic, or metal spacer is inserted between the new ball and the socket.

• THA is the primary treatment for end-stage degenerative hip osteoarthritis (OA) for pain relief and functional restoration. The incidence of hip OA is 88 symptomatic cases per 100,000 patients per year. Other underlying diagnoses include hip osteonecrosis (ON), congenital hip disorders, and inflammatory arthritis, which account for 10% of annual THAs.
• About 70% of THA dislocations occur within the first month following index surgery. The overall incidence is about 1% to 3%. Risk factors for dislocation post-surgery include prior hip surgery, older than 70 years of age, component malpositioning, neuromuscular disorders, and drug/alcohol use.
• The surgical approach is associated with the risk for dislocation with the lateral approach having the lowest dislocation rate at 0.55%, compared to 3.23% for the posterior approach.

https://www.ncbi.nlm.nih.gov/books/NBK507864/

Trochanteric Bursitis: Trochanteric bursitis is a common cause of lateral hip pain caused by inflammation of the trochanteric bursa, which lies superficial to the hip abductor musculature and deep to the iliotibial band. The bursitis can be caused by acute trauma including falling on the hip with direct compression of the bursa, due to repetitive microtraumas incurred from running, cycling, stair climbing, or other repetitive hip movements, or caused by anatomical features like females with increased Q angles which leads to tighter IT bands producing stress over the bursa.

• Trochanteric bursitis is transmodal in distribution affecting those of all ages.
• Data suggests that trochanteric bursitis can affect up to 15% of women and 8% of men.

https://www.ncbi.nlm.nih.gov/books/NBK538503/

Anterior Cruciate Ligament (ACL) Tear: The ACL is one of the primary stabilizing ligaments of the knee that extends form the anteriomedial tibial plateau of the intercondylar eminence running posterior and lateral to attach to the medial aspect of the lateral femoral condyle. The ACL is the most commonly injured ligament in the body for which surgery is performed. The injury is typically sports based when the non-contact mechanism of sudden changes in direction of movement, rapid stopping, jumping and landing abnormally, or a direct blow to the lateral aspect of the knee are applied causing rotary forces at the knee.

• The annual reported incidence in the United States alone is approximately 1 in 3500 people. However, data may not be accurate as there is no standard surveillance.
• It is estimated that 175,000 ACL reconstructions were performed in the year 2000 in the US, ¹at a cost of more than two billion dollars.
• When considering sports or activities in which both sexes participated, women had a significantly higher incidence ratio than men (incidence ratio1.5).
• The majority of ACL tears (67% in men and almost 90% in women) occurred without contact.
• Besides the immediate associated morbidity and costs, an ACL tear significantly increases the risk for premature knee osteoarthritis (OA). It is estimated that 50% of patients with ACL tears develop osteoarthritis 10 to 20 years later.
• An “isolated” ACL tear occurs less than 10% of the time with an assessment needed for diagnosis of associated injuries. The prevalence of associated meniscus injuries is 60% to 75%;articular cartilage injuries, up to 46%,subchondral bone injuries (i.e., “bone bruises” on MRI), 80%^, and complete collateral ligament tears (medial or lateral), 5 to 24%.
• According to a recent systematic review, utilizing arthroscopy as the gold standard ACL tear diagnosis, MRI had a sensitivity of 86%, specificity of 95%, and accuracy of 93% for ACL tear.
• Two physical exam maneuvers-- the Lachman test and the pivot shift test-- are useful in assessment for ACL tear. In a recent meta-analysis of 28 studies, the pooled sensitivity and specificity of the Lachman test for ACL tear was 85% and 94%, respectively.For the pivot shift, specificity was high (98%) but sensitivity was low (24%). 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3782299/

https://www.ncbi.nlm.nih.gov/books/NBK499848/

Chondromalasia Patella: Chrondromalasia patella is the softening and subsequent breakdown – tearing, fissuring, and erosion of hyaline cartilage – of the hyaline cartilage of the undersurface of the patella. As such, it is sometimes referred to as patellofemoral syndrome, or runner’s knee. Post-traumatic injuries, microtrauma wear and tear (including from patellofemoral malalignment), and iatrogenic injections of medication can lead to the development of chondromalacia. 

• More women than men are affected, and this is attributed to increased Q angles in women. There does not appear to be a hormonal cause of variation. 
• Patients with knee pain resulting from chondromalacia patella often achieve full recovery. Recovery can occur in as little as a month or take years, depending on the case. Teenagers often achieve long-term recovery because their bones are still growing, and their symptoms generally ameliorate after reaching adulthood.

https://www.ncbi.nlm.nih.gov/books/NBK459195/

Iliotibial Band Syndrome (ITBS): The iliotibial band is the fascial continuation of the tensor fascia latae muscle that terminates with its insertion onto Gerdy’s tubercule on the anterolateral aspect of the lateral tibial plateau. As one of the many common causes of lateral knee pain (between Gerdy’s tubercle and lateral epicondyle for ITBS), ITBS is thought to be caused by a tightness if the iliotibial band. One theory for the pain is that the tightness of the ITB causes compression of the highly innervated fat pad that is deep to the distal ITB. Another theory states that there is repetitive friction irritation (repeated knee flexion and extension) of the ITB as it crosses the lateral femoral epicondyle. There is also the theory that the repetitive motion irritates and inflames the fluid filled ITB bursae located between the ITB and lateral femoral epicondyle.

• ITBS is the most common etiology of lateral knee pain in runners and cyclists but may also present in athletes participating in tennis, soccer, skiing, and weight lifting.
• The incidence ranges from 1.6% to 12% in runners and other repetitive motion athletes.
• It is slightly more common in women than men and seldom occurs in the non-active population.
• One cross-sectional study demonstrated that the incidence of ITBS was 6.2% in military recruits. The U.S. Marine Corps reported running/overuse injuries accounted for 12% of injuries sustained by their personnel.
• Roughly 50% to 90% of patients will improve with 4 to 8 weeks of non-operative therapeutic intervention.

https://www.ncbi.nlm.nih.gov/books/NBK542185/

Knee Arthroplasty: The knee is the most commonly affected joint plagued by degenerative osteoarthritis and loss of articular cartilage, and total knee arthroplasty (TKA) provides successful outcomes for those with end-stage arthritis by resurfacing the damaged articulating surfaces of the knee.

• Estimates project the annual incidence of symptomatic knee OA at 240 per 100,000 patients per year, and about 400,000 primary TKA surgeries are performed annually in the United States.
• The most common clinical diagnosis associated with TKA is primary OA, but other potential underlying diagnoses include inflammatory arthritis, fracture (post-traumatic OA and/or deformity), dysplasia, and malignancy.

https://www.ncbi.nlm.nih.gov/books/NBK499896/

Lateral Collateral (fibular) Ligament (LCL) Tear: The LCL is one of the primary stabilizers of the knee joint that attaches to the lateral femoral epicondyle to the head of the fibula. Its primary function is to prevent excess varus stress and posterior-lateral rotation of the knee, and its most common mechanism of injury is a significant impact to the anteromedial knee producing a combined hyperextension and extreme varus force.

• Due to its close association with the PLC, PCL, and ACL, the LCL is rarely ever injured in isolation. Studies show that isolated LCL injuries in high school athletes are second to last in incidence at 7.9%. PCL injuries are the least common, at 2.4%.
• Reportedly, 40% of PLC and LCL injuries are due to contact sports. Other instances are due to trauma, motor vehicle accidents, and falls.
• Specific to evaluation and diagnosis, MRI coronal and sagittal T1 and T2 weighted series have the highest sensitivity and specificity for LCL injury (approximately 90%).

https://www.ncbi.nlm.nih.gov/books/NBK560847/

Medial Collateral (tibial) Ligament (MCL) Tear: The MCL is a flat band ligamentous tissue that runs from the medial epicondyle of the femur to the medial condyle of the tibia whose role is to provide stability against excess valgus stress to the knee. The mechanism of injury may involve abrupt turning, cutting, or twisting. MCL injuries can also result from direct blows to the lateral knee that cause an extreme valgus stress. Injuries to the MCL can be isolated but more commonly will occur in conjunction with injuries to other knee structures.

• Ligament injuries of the knee account for approximately 40 percent of all knee injuries, and of these, medial collateral ligament (MCL) injuries are the most common.
• Sixty percent of skiing knee injuries involve the MCL.
• The MCL is injured in at least 42% of ligamentous knee injuries, with isolated MCL injuries accounting for 29% of these injuries alone.
• In the U.S. population, the incidence of MCL injury is 0.24/1000 people or 74,000 injuries annually.

https://www.ncbi.nlm.nih.gov/books/NBK431095/

https://now.aapmr.org/medial-and-lateral-collateral-ligament-injuries/

Meniscal Tear (Medial and Lateral): The medial and lateral menisci are crescent-shaped fibrocartilaginous structures that sit atop the medial and lateral tibial plateaus covering approximately 70% of the articular surface area and bear approximately 70% of the load transmission of the body weight and provides shock absorption for the knee joint. Isolated meniscal tears occur due to rotational or shearing forces placed across the tibiofemoral joint, especially when an increased axial load is placed through the menisci.

• Studies in the United States have indicated a 61 per 100,000 incidence rate of meniscal tears in the general population and up to an 8.7 per 1,000 incidence rate in the active-duty military population.
• Medial meniscal tears are more common than lateral meniscal tears, possibly due to the relatively decreased mobility of the medial meniscus secondary to its connection to the MCL.
• People with ACL-deficient knees are more at risk for the development of medial meniscal tears, especially if ACL reconstruction is delayed for longer than one year from the time of initial injury.
• MRI imaging has been found to be 93% sensitive and 88% specific for medial meniscal tears, and 79% sensitive and 96% specific for lateral meniscal tears.

https://www.ncbi.nlm.nih.gov/books/NBK431067/

Meniscectomy: Meniscectomy is the arthroscopic surgical procedure to remove all or part of a torn meniscus, with the goal to relieve pain and possible “catching” at the knee, return to normal pre-injury ADL and athletic activities, and to prevent early degeneration/arthritis of the knee.

• Approximately 61 in 100,000 meniscal injury patients undergo meniscectomy.
• Between 500,000 to 750,000 partial meniscectomy surgeries are performed annually in the United States.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3438273/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5990328/

Patellar Tendonitis: Patellar tendonitis is an injury to and inflammation of the patellar tendon connecting the patella to the tibial tuberosity of the tibia. Also known as jumpers knee, patellar tendonitis is most common in athletes whose sports involve frequent jumping.

• The prevalence of patellar tendinopathy in nonelite athletes ranges from 11.8% to 14.4%.
• Patellar or patellar tendon injuries have been reported to account for 29.5% of all knee injuries in high school athletes.
• Patellofemoral injury accounts for 10.1% of all injuries in professional basketball players and 10.2% of all knee injuries in professional baseball players.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6481003/

Patellofemoral Syndrome (PFS): Patellofemoral syndrome (PFS), also commonly known as runner’s knee or patellofemoral pain syndrome, is one of the most common causes of anterior knee pain, with the pain typically located behind or around the patella and aggravated by loading a flexed knee joint – running, climbing stairs, and squatting. Studies point to four major contributing factors: malalignment of the lower extremity and/or patella, muscular imbalance of the lower extremity, overactivity/overload, and trauma.

• Overactivity appears to be the most important contributing factor to the development of the condition.
• In active individuals, it may account for 25% to 40% of all knee problems seen in a sports medicine clinic.
• PFS affects women more so than men at a ratio of close to 2:1.
• Age of occurrence is typically seen in adolescents and adults in the second and third decades of life. Its prevalence in adolescence was found to be over 20%.

https://www.ncbi.nlm.nih.gov/books/NBK557657/

Posterior Cruciate Ligament (PCL) Tear: The PCL is one of the primary stabilizing ligaments of the knee that extends form the posterior aspect of the tibial plateau to the anterolateral aspect of the medial femoral condyle in the area of the intercondylar notch. It primarily functions to prevent posterior translation of the tibia on the femur, but also contributes to resist varus, valgus, and external rotation forces. It is approximately 1.3 to 2 times as thick and about twice as strong as the anterior cruciate ligament (ACL) and, consequently, less commonly subject to injury.

• Injuries to the PCL are caused by an extreme anterior force applied to the proximal tibia of the flexed knee – dashboard impact in motor vehicle accidents (45%), falling forward onto a flexed knee during athletic events (40%). Specifically, the two most common causes of injury are motorcycle accidents (28%) and soccer-related injuries (25%). The most common injury mechanism was dashboard injuries (35%) and falls on a flexed knee with the foot in plantar flexion (24%).
• According to a 2003 study by Schulz et al., the mean age of PCL injuries was 27 years.
• The male to female ratio is 2:1. 
• MRI is the gold standard for the evaluation of a PCL injury. It has been reported to have accuracy in the range of 96% to 100%.

https://www.ncbi.nlm.nih.gov/books/NBK430726/

Achilles Tendinitis: The Achilles tendon is the common tendon connecting the gastrocnemius and soleus muscles to the calcaneus bone and is the strongest tendon in the human body. Achilles tendinitis is an overuse injury to the tendon causing pain and inflammation.

• The Achilles tendon has a cumulative lifetime injury incidence of approximately 24% in athletes. Running-related injuries have a prevalence between 11% and 85% or 2.5 to 59 injuries per 1000 hours of running.
• The lifetime injury incidence of 2.35 per 1000 is strongly associated with sporting activities.
• The lifetime injury incidence of 2.35 per 1000 is strongly associated with sporting activities.

https://www.ncbi.nlm.nih.gov/books/NBK538149/

https://medlineplus.gov/ency/article/001072.htm

Achilles Tendon Rupture: The Achilles tendon is the common tendon connecting the gastrocnemius and soleus muscles to the calcaneus bone and is the strongest tendon in the human body. A rupture to the tendon is usually caused by a forceful weight-bearing dorsiflexion mechanism that overstretches the tendon and is often associated with an audible loud pop.

• Achilles tendon rupture is the most common tendon rupture in the lower extremity.
• Achilles tendon injuries typically occur in individuals who are only active intermittently.
• Moreover, patients in their third to the fifth decade of life are most commonly affected as 10% report a history of prodromal symptoms, and known risk factors include prior intratendinous degeneration (i.e., tendinosis), fluoroquinolone use, steroid injections, and inflammatory arthritides.
• The incidence rates of Achilles tendon ruptures varies in the literature, with recent studies reporting a rate of 18 patients per 100,000 patient population annually.
• In regard to athletic populations, the incidence rate of Achilles tendon injuries ranges from 6% to 18%, and football players are the least likely to develop this problem compared to gymnasts and tennis players. It is believed that about a million athletes suffer from Achilles tendon injuries each year.

https://www.ncbi.nlm.nih.gov/books/NBK430844/

Ankle Sprain:An ankle sprain occurs when you roll or twist your ankle resulting in damage to the stabilizing ligaments of the ankle and subtalar joints causing pain, swelling, restricted range of motion, and short term disability. Inversion ankle sprains (foot turns inward) are far more common than eversion ankle sprains (foot turns outward).

• More than three-quarters of all acute ankle sprains are lateral ankle sprains, and approximately 73% of these are injuries to the anterior talofibular ligament. The remaining ∼25% of all acute ankle sprains are medial (deltoid ligament) or high ankle/syndesmosis (anterior-inferior tibiofibular ligament or posterior-inferior tibiofibular ligament injuries).
• A sprain of the lateral ankle ligament complex is the most common type of ankle sprain; the authors of a meta-analysis estimated an incidence rate of 0.93/1000 athlete-exposures (AEs; 1 AE is defined as 1 athlete participating in 1 competition or practice). In comparison, the reported incidence rates of acute medial and high/syndesmotic ankle sprains were lower at approximately 0.06 and 0.38/1000 AEs, respectively.
• Many studies comparing sex-comparable sports note a similar incidence rate for ankle sprains when comparing male and female athletes. 
• Furthermore, multiple studies report the high rate of recurrent injuries and recurrent instability in patients sustaining a single primary ankle sprain, and up to 40% of patients sustaining a lateral ankle sprain note persistent symptoms, recurrent sprains, and chronic lateral ankle instability.
• In the United States, approximately 2 million acute ankle sprains occur annually.
• Data from emergency department visits suggest an incidence rate of 2 to 7 acute ankle sprains/1000 person-years.

https://pubmed.ncbi.nlm.nih.gov/31135209/

https://www.ncbi.nlm.nih.gov/books/NBK459212/

Anterior Tibial Compartment Syndrome: Anterior tibial compartment syndrome occurs when the tissue pressure within a given compartment exceeds the perfusion pressure of the arterial supply, resulting in ischemia of the muscles and nerves of the compartment and the potential loss of nerve function and associated muscle activation. The etiology is varied; however, most commonly it is related to acute trauma or overuse syndrome. The anterior tibial compartment contains the tibialis anterior, extensor digitorum longus, extensor hallucis longus, and fibularis tertius muscles which are primarily responsible for ankle dorsiflexion and inversion and are innervated by the deep fibular nerve.

• Tibial fracture is the most common cause of compartment syndrome accounting for up to 12% of all compartment syndrome cases.
• Open tibial fractures are more likely to cause compartment syndrome (6%) than closed fractures (1.2%).
• In patients with tibial diaphyseal fractures, younger age is associated with an increased risk of developing compartment syndrome. Increased fracture length relative to the length of the tibia is associated with increased risk.
• The incidence of chronic exertional compartment syndrome is a relatively common cause of leg pain in athletes ranging from 27% to 33%. Risk factors include running athletes. Also, fascia defects occur in up to 40% of athletes compared to 5% in asymptomatic athletes. Symptoms are frequently bilateral. Males and females are affected equally.

https://www.ncbi.nlm.nih.gov/books/NBK518970/

Medial Tibial Stress Syndrome (MTSS): Medial Tibial Stress Syndrome (MTSS), also known as shin splints, is a common overuse injurie of the lower extremity, often seen in athletes and military personnel. It involves exercise-induced pain over the anterior tibia and is an early stress injury in the continuum of tibial stress fractures. Medial tibial stress syndrome is an overuse condition, specifically a tibial bony overload injury with associated periostitis.

• The incidence of medial tibial stress syndrome ranges between 13.6% to 20% in runners and up to 35% in military recruits.
• Intrinsic risk factors include increases in the female gender, previous history of MTSS, high BMI, navicular drop (a measure of arch height and foot pronation), ankle plantar flexion range of motion, and hip external rotation range of motion.

https://www.ncbi.nlm.nih.gov/books/NBK538479/

Claw, Hammer, Mallet Toes: All three of these toe deformities affect one or more of the joints of the toe, but in different patterns. Claw toe involves the hyperextension of the metatarsophalangeal (MTP) joint and the hyperflexion of the proximal interphalangeal (PIP) and distal interphalangeal (DIP) joint. Hammer toe involves hyperextension of the MTP joint, flexion of the PIP joint, and extension of the DIP joint. Mallet toe is simply a hyperflexion of the DIP joint. These conditions can be the result of nerve damage by diseases like diabetes or alcoholism and weakening of various foot muscles.

https://pubmed.ncbi.nlm.nih.gov/32644694/

Diabetic Foot Syndrome (DFS): DFS is a major complication of diabetes mellitus and is defined as an ulceration of the foot associated with neuropathy and different grades of ischemia and infection.

• Among diabetic vascular complications, foot ulcers represent the first cause of hospitalization in diabetics and a significant cause of health care costs (more than 20%-40% of health care resources have been reported as related to diabetes-related foot care).
• More than 80,000 amputations directly related to diabetes have been registered in the United States annually and the majority (80%) of these have been performed in patients with a previous foot ulceration.
• It has been estimated that 15% of patients with diabetes will develop a lower extremity complication in their life. Some authors reported a 0.5% to 3% incidence of diabetic foot ulcers, whereas foot ulcer prevalence, as reported by some population surveys, ranges from 2% to 10%.
• More than 15% of patients with DFS experienced a lower limb amputation and some authors reported that survival rate in patients that undertaken a lower limb amputation is significantly shorter and more than $ 2700 is the cost for a 2-year care of a new-diagnosed foot ulcer.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4303791/

Fracture (5^th Metatarsal): The 5^th metatarsal bone is divided into three anatomical zones: zone 1, the tuberosity; zone 2, the metaphyseal-diaphyseal junction; and zone 3, the diaphyseal area within 1.5 cm of the tuberosity. Fractures through zone 1 have the name to as pseudo-Jones fractures, and fractures through zone 2 are referred to as Jones fractures. Additionally, a patient may sustain a shaft fracture greater than 1.5 cm distal to the tuberosity, a long spiral fracture extending into the distal metaphyseal area, the so-called dancer's fracture, or a stress fracture of the metatarsal.

• Fractures of the fifth metatarsal are the most prevalent metatarsal fractures. 
• These fractures peak during the third decade of life for men and the seventh decade of life for women. There is a strong correlation between female gender and zone 1 fractures and dancer's fractures. Zone 1 injuries are typical of a twisting injury and are the most common fracture of the base of the fifth metatarsal.
• The majority of acute, nondisplaced fractures of the fifth metatarsal heal with conservative treatment by 6 to 8 weeks. Zones 2 and 3 injuries have a higher rate of nonunion due to the vascular watershed area mentioned earlier, with zone 2 injuries having a nonunion rate as high as 15 to 30%. 

https://www.ncbi.nlm.nih.gov/books/NBK544369/

Hallux Valgus (HV) and Bunion: Hallux valgus is a complex deformity of the first metatarsal resulting in a lateral deviation of the great toe and the first metatarsal head deviating medially. This deformity can develop a bunion, a red and painful inflammatory condition on the medial aspect of the first metatarsophalangeal joint. Hallux valgus deformity is most likely a result of multiple contributing factors including genetics, short first metatarsal, dorsiflexed first metatarsal, flexible or rigid forefoot varus, rigid or flexible pes planovalgus, gastrocnemius equinus, abnormal foot mechanics, and joint hypermobility.

• Occurs in approximately 23% of adults aged 18 to 65 years and up 36% of adults older than 65 years old.
• When looking at adult females, HV deformity occurs as high as 30%.

https://www.ncbi.nlm.nih.gov/books/NBK553092/

Hallux Varus: Hallux varus is characterized by medial deviation of the great toe at the metatarsophalangeal (MTP) joint.

• Adult acquired hallux varus deformity is commonly iatrogenic, occurring as a result of surgery for hallux valgus. The incidence of iatrogenic postoperative hallux varus varies from 2% to 14% after corrective surgery for hallux valgus deformity.
• the incidence of idiopathic, congenital/infantile, traumatic, and otherwise acquired hallux varus is unknown.

https://www.ncbi.nlm.nih.gov/books/NBK470261/

Lis Franc Injury: A Lisfranc injury describes a spectrum of injuries involving the tarsometatarsal joints of the foot. The Lisfranc joint is comprised of the articulation between the first, second, and third metatarsals bones and the cuneiform bones. Injuries of the joint can range from complete tarsometatarsal displacement with associated fractures and ligamentous tears to partial sprains with no displacement. There are usually two main mechanisms that cause this type of injury: direct, and indirect. A direct mechanism of injury occurs as a crush injury to the joint region from an event such as a motor vehicle collision or industrial accident. An indirect injury is more common than a direct injury and is often associated with sports participation. This mechanism of injury usually involves a longitudinal force while the foot is plantar flexed with a medial or lateral rotational force.

• They account for 0.2% of all fractures, but the prevalence is likely higher as these frequently go undiagnosed. The reported incidence of this injury is approximately 1 per 55,000 persons per year.
• This injury can occur in all ages but is more common in the third decade of life and is more common in males. Lisfranc injuries occur more frequently in athletes and have become increasingly diagnosed in this group.

https://www.ncbi.nlm.nih.gov/books/NBK448147/

Peroneal Tendon Pathology: Peroneal tendon disorders are a cause of hindfoot and lateral foot pain. There are three primary disorders of the tendons; Peroneal tendonitis, peroneal subluxation, and peroneal tendon tears. These conditions are a cause of lateral ankle pain and may lead to ankle instability. The peroneal tendons are in the lateral compartment of the leg and include the peroneus longus and peroneus brevis muscles.

• The most common patient population with tears of the peroneal tendons are active young patients. Tears are more likely to be longitudinal due to subluxation over the fibula, but can also be transverse. 
• A retrospective review of peroneal tendon tears showed brevis tears in 88% of patients, longus tears in 13% of patients and combined peroneus longus and brevis tears in 37%.
• Saxena showed 87% return to the sport in a case series of operatively treated tears. Post-op repair of peroneal tendon tears in a retrospective review by Dombek showed that 98% of patients returned to full activities at an average follow up of 13 months.
• Outcomes for operative treatment of tendon subluxation are good with Saxena showing a 100% return to sport after repair of the superior retinacular ligament.

https://www.ncbi.nlm.nih.gov/books/NBK544354/

Pes Planus (Flat Foot): Pes planus is a relatively common foot deformity that refers to the loss of the medial longitudinal arch of the foot, resulting in this region of the foot coming closer to the ground or making contact with the contacting the ground.

• Congenital Pes planus is fairly common in infants with most children developing normal arches by age 5 or 6. Obesity in children is significantly correlated with the tendency of the longitudinal arch to collapse in early childhood.
• Acquired Pes Planus is most commonly occurs secondary to posterior tibial tendon dysfunction. Posterior tibial tendon dysfunction is most common in females over the age of 40 with comorbidities, including diabetes and obesity.
• It is estimated that about 20% to 37% of the population has some degree of pes planus, with a majority being flexible pel planus.

https://www.ncbi.nlm.nih.gov/books/NBK430802/

Pes Cavus (High Arch): Pes planus is typically characterized by the elevation of the longitudinal arch of the foot, plantar flexion of the first metatarsal, forefoot pronation, and valgus, hindfoot varus, and forefoot adduction.

• Pes cavus is seen in both adult and pediatric populations.
• When it is found to be bilateral, it is often from a hereditary or congenital source.
• Pes cavus typically presents in adolescence or early adulthood and is often a sign of an underlying neurological disease. 

https://www.ncbi.nlm.nih.gov/books/NBK556016/

Plantar Calcaneal Spur (PCS): a bony outgrowth on the plantar surface of the calcaneus that prevents with heel pain(over 50% of cases) and is often accompanied by plantar fasciitis (present in 45–85% of those with plantar fasciitis). The etiology of these spurs is a contentious issue, and it has been explained through a number of theories including the degenerative, inflammatory, traction, repetitive trauma, bone‐formers and vertical compression theories. 

• Studies have shown that calcaneal bone spurs are more common in women and older patients and that patients with spurs were 4 times more likely to have diabetes mellitus and 10 times more likely to have lower-limb osteoarthritis.
• In the young to middle‐aged population PCS prevalence is 11–21%. This is constant across various ethnicities with rates of 11% in India, 13% in Ireland, 15% in Zimbabwe, 16% in Thailand, 17% in Europe and 21% in America.
• The prevalence of PCS increases in older age groups, weight, foot pronation deviation (62% of patients with a spur and 81% with a painful spur having a pronated foot radiographically), arthritis (estimates as high as 80% in osteoarthritis and 72% in rheumatology patients over 61 years)

https://pubmed.ncbi.nlm.nih.gov/24379452/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5442149/

Plantar Fasciitis: Plantar fasciitis is the result of degenerative irritation of the plantar fascia origin at the medial calcaneal tuberosity of the heel as well as the surrounding perifascial structures. It is often an overuse injury that is primarily due to a repetitive strain causing micro-tears of the plantar fascia but can occur as a result of trauma or other multifactorial causes. It is often associated with runners and older adults, but other risk factors include obesity, heel pad atrophy, aging, occupations requiring prolonged standing, and weight-bearing.

• Approximately 50% of patients with this condition will also have heel spurs, but the spurs themselves are not the cause. 
• This condition accounts for about 10% of runner-related injuries and 11% to 15% of all foot symptoms requiring professional medical care. 
• It is thought to occur in about 10% of the general population as well, with 83% of these patients being active working adults between the ages of 25 and 65 years old. 
• It may present bilaterally in a third of the cases.

https://www.ncbi.nlm.nih.gov/books/NBK431073/

Tarsal Tunnel Syndrome: Tarsal tunnel syndrome, sometimes called tibial nerve dysfunction, is a disorder where there is a compression of the posterior tibial nerve, which runs behind and inferior to the medial malleolus, and is characterized by pain in the ankle, foot, and toes. The nerve compression is usually caused by inflammation of the tissues around the nerve, namely the tendons of the posterior tibialis, flexor digitorum longus, and flexor hallucis longus.

• The mechanism of compression/impingement can be identified in approximately 80% of cases.
• Up to 43% of patients have a history of trauma including events such as ankle sprains. Abnormal biomechanics can contribute to disease progression. Risk factors include systemic diseases such as diabetes mellitus, hypothyroidism, gout, mucopolysaccharidosis, and hyperlipidemia.

https://www.ncbi.nlm.nih.gov/books/NBK513273/