Tendon injury and resulting tendinopathy are responsible for up to 30% of consultations to sports doctors and other musculoskeletal health providers. Tendinopathy is most often seen in tendons of athletes either before or after an injury but is becoming more common in non-athletes and sedentary populations. For example, the majority of patients with Achilles tendinopathy in a general population-based study did not associate their condition with a sporting activity. In another study the population incidence of Achilles tendinopathy increased sixfold from 1979-1986 to 1987-1994. The incidence of rotator cuff tendinopathy ranges from 0.3% to 5.5% and annual prevalence from 0.5% to 7.4%.

In tennis players, about 39.7% have reported current or previous problems with their elbow. Less than one quarter (24%) of these athletes under the age of 50 reported that the tennis elbow symptoms were "severe" and "disabling," while 42% were over the age of 50. More women (36%) than men (24%) considered their symptoms severe and disabling. Tennis elbow is more prevalent in individuals over 40, where there is about a four-fold increase among men and two-fold increase among women. Tennis elbow equally affects both sexes and, although men have a marginally higher overall prevalence rate as compared to women, this is not consistent within each age group, nor is it a statistically significant difference.

Playing time is a significant factor in tennis elbow occurrence, with increased incidence with increased playing time being greatery for respondents under 40. Individuals over 40 who played over two hours doubled their chance of injury. Those under 40 increased it 3.5 fold compared to those who played less than two hours per day.

Another factor of tennis elbow injury is experience and ability. The proportion of players who reported a history of tennis elbow had an increased number of playing years. As for ability, poor technique increases the chance for injury much like any sport. Therefore, an individual must learn proper technique for all aspects of their sport. The competitive level of the athlete also affects the incidence of tennis elbow. Class A and B players had a significantly higher rate of tennis elbow occurrence compared to class C and novice players. However, an opposite, but not statistically significant, trend is observed for the recurrence of previous cases, with an increasingly higher rate as ability level decreases.

Other ways to prevent tennis elbow:

- Decrease the amount of playing time if already injured or feeling pain in outside part of the elbow.

- Stay in overall good physical shape.

- Strengthen the muscles of the forearm: (pronator quadratus, pronator teres, and supinator muscle)—the upper arm: (biceps, triceps)—and the shoulder (deltoid muscle) and upper back (trapezius). Increased muscular strength increases stability of joints such as the elbow.

- Like other sports, use equipment appropriate to your ability, body size, and muscular strength.

- Avoid any repetitive lifting or pulling of heavy objects (especially over your head)

Vibration dampeners (otherwise known as "gummies") are not believed to be a reliable preventative measure. Rather, proper weight distribution in the racket is thought to be a more viable option in negating shock.

The most common examples of this condition:

- Prepatellar bursitis, "housemaid's knee"

- Infrapatellar bursitis, "clergyman's knee"

- Trochanteric bursitis, giving pain over lateral aspect of hip

- Olecranon bursitis, "student's elbow", characterised by pain and swelling in the elbow

- Subacromial bursitis, giving shoulder pain, is the most common form of bursitis.

- Achilles bursitis

- Retrocalcaneal bursitis

- Ischial bursitis, "weaver's bottom"

- Iliopsoas bursitis

- Anserine bursitis

There can be several concurrent causes. Trauma, auto-immune disorders, infection and iatrogenic (medicine-related) factors can all cause bursitis. Bursitis is commonly caused by repetitive movement and excessive pressure. Shoulders, elbows and knees are the most commonly affected. Inflammation of the bursae may also be caused by other inflammatory conditions such as rheumatoid arthritis, scleroderma, systemic lupus erythematosus and gout. Immune deficiencies, including HIV and diabetes, can also cause bursitis. Infrequently, scoliosis can cause bursitis of the shoulders; however, shoulder bursitis is more commonly caused by overuse of the shoulder joint and related muscles.

Traumatic injury is another cause of bursitis. The inflammation irritates because the bursa no longer fits in the original small area between the bone and the functionary muscle or tendon. When the bone increases pressure upon the bursa, bursitis results. Sometimes the cause is unknown. It can also be associated with various other chronic systemic diseases.

The condition is called "Golfer's Elbow" because in making a golf swing this tendon is stressed, especially if a non-overlapping (baseball style) grip is used; many people, however, who develop the condition have never handled a golf club. It is also sometimes called "Pitcher's Elbow" due to the same tendon being stressed by the throwing of objects such as a baseball, but this usage is much less frequent. Other names are "Climber's Elbow" and "Little League Elbow": all of the flexors of the fingers and the pronators of the forearm insert at the medial epicondyle of the humerus to include: pronator teres, flexor carpi radialis, flexor carpi ulnaris, flexor digitorum superficialis, and palmaris longus; making this the most common elbow injury for rock climbers, whose sport is very grip intensive. The pain is normally caused due to stress on the tendon as a result of the large amount of grip exerted by the digits and torsion of the wrist which is caused by the use and action of the cluster of muscles on the condyle of the ulna.

Epicondylitis is much more common on the lateral side of the elbow (tennis elbow), rather than the medial side. In most cases, its onset is gradual and symptoms often persist for weeks before patients seek care. In golfer's elbow, pain at the medial epicondyle is aggravated by resisted wrist flexion and pronation, which is used to aid diagnosis. On the other hand, tennis elbow is indicated by the presence of lateral epicondylar pain precipitated by resisted wrist extension. Although the condition is poorly understood at a cellular and molecular level, there are hypotheses that point to apoptosis and autophagic cell death as causes of chronic lateral epicondylitis. The cell death may decrease the muscle density and cause a snowball effect in muscle weakness - this susceptibility can compromise a muscle's ability to maintain its integrity. So athletes, like pitchers, must work on preventing this cell death via flexibility training and other preventive measures.

Several risk factors of CMC OA of the thumb are known. Each of these risk factors does not cause CMC OA by itself, but acts as a predisposing factor influencing the process of OA in some way. Risk factors include: female gender, suffering from obesity, repetitive heavy manual labor, familial predisposition and hormonal changes, such as menopause.

It is an overuse injury from repetitive overloading of the extensor mechanism of the knee. The microtears exceed the body's healing mechanism unless the activity is stopped.

Among the risk factors for patellar tendonitis are low ankle dorsiflexion, weak gluteal muscles, and muscle tightness, particularly in the calves, quadriceps muscle, and hamstrings.

The injury occurs to athletes in many sports.

In horses tendinitis is called a bowed tendon from the appearance of the affected tendon after it heals without treatment. Mesenchymal stem cells, derived from a horse's bone marrow or fat, are currently being used for tendon repair in horses.

The exact etiology of tendinopathy has not been fully elucidated and different stresses may induce varying responses in different tendons. There are multifactorial theories that could include: tensile overload, tenocyte related collagen synthesis disruption, load-induced ischemia, neural sprouting, thermal damage, and adaptive compressive responses. The intratendinous sliding motion of fascicles and shear force at interfaces of fascicles could be an important mechanical factor for the development of tendinopathy and predispose tendons to rupture. Obesity, or more specifically, adiposity or fatness, has also been linked to an increasing incidence of tendinopathy.

The most commonly accepted cause for this condition however is seen to be an overuse syndrome in combination with intrinsic and extrinsic factors leading to what may be seen as a progressive interference or the failing of the innate healing response. Tendinopathy involves cellular apoptosis, matrix disorganization and neovascularization.

Tendinopathy can be induced in animal models by a surgical injury to the tendon. In both sheep shoulder (infraspinatus) and horse forelimb (superficial digitor flexor) tendons, a mid-tendon transection caused pathology in the entire tendon after four and six weeks respectively.

Quinolone antibiotics are associated with increased risk of tendinitis and tendon rupture. A 2013 review found the incidence of tendon injury among those taking fluoroquinolones to be between 0.08 and 0.2%. Fluoroquinolones most frequently affect large load-bearing tendons in the lower limb, especially the Achilles tendon which ruptures in approximately 30 to 40% of cases.

CMC OA is the most common form of OA affecting the hand. Dahaghin et al. showed that about 15% of women and 7% of men between 50 and 60 years of age suffer from CMC OA of the thumb. However, in about 65% of people older than 55 years, radiologic evidence of OA was present without any symptoms. Armstrong et al. reported a prevalence of 33% in postmenopausal women, of which one third was symptomatic, compared to 11% in men older than 55 years. This shows CMC OA of the thumb is significantly more prevalent in women, especially in postmenopausal women, compared to men.

Tendinosis of the common extensor tendon of the elbow (“tennis elbow”), as of the Rotator Cuff, is a common cause of pain in the elbow or shoulder.

The general opinion is that tendinosis is due to tendon overuse, and failed healing of the tendon. In addition, the extensor carpi radialis brevis muscle plays a key role.

According to the International Classification of Diseases, 9th Revision, Clinical Modification, ICD-9-CM, in 2008 the U.S. listed the diagonsis code for UCL injury as 841.1: Sprain ulnar collateral ligament. There were a total of 336 discharges of UCL injuries. Within the total discharges, separated by age groups: 18- to 44-year-olds; 165 people (49.17%). 45- to 64-year-olds; 91 (27.08%). 65- to 84-year-olds, 65 (19.35%) it shows that the ulnar collateral ligament injuries were more commonly found in men than women. There were 213 men compared to 123 women with ulnar collateral ligament injury. Most of these injuries were also paid through private insurance (170: 50.63%) and Medicare (70: 20.85%). The average estimated cost for the surgery also known as Tommy John surgery is $21,563.

Tendinitis injuries are common in the upper shoulder and lower section of the elbow (including the rotator cuff attachments), and are less common in the hips and torso. Individual variation in frequency and severity of tendinitis will vary depending on the type, frequency and severity of exercise or use; for example, rock climbers tend to develop tendinitis in their fingers or elbows, swimmers in their shoulders. Achilles tendinitis is a common injury, particularly in sports that involve lunging and jumping, while Patellar tendinitis is a common among basketball and volleyball players owing to the amount of jumping and landing.

A veterinary equivalent to Achilles tendinitis is bowed tendon, tendinitis of the superficial digital tendon of the horse.

Golfer's elbow, or medial epicondylitis, is tendinosis of the medial epicondyle on the inside of the elbow. It is in some ways similar to tennis elbow, which affects the outside at the lateral epicondyle.

The anterior forearm contains several muscles that are involved with flexing the digits of the hand, and flexing and pronating the wrist. The tendons of these muscles come together in a common tendinous sheath, which originates from the medial epicondyle of the humerus at the elbow joint. In response to minor injury, or sometimes for no obvious reason at all, this point of insertion becomes inflamed.

Tendinosis, sometimes called chronic tendinitis, chronic tendinopathy, or chronic tendon injury, is damage to a tendon at a cellular level (the suffix "osis" implies a pathology of chronic degeneration without inflammation). It is thought to be caused by microtears in the connective tissue in and around the tendon, leading to an increase in tendon repair cells. This may lead to reduced tensile strength, thus increasing the chance of tendon rupture. Tendinosis is often misdiagnosed as tendinitis because of the limited understanding of tendinopathies by the medical community. Classic characteristics of "tendinosis" include degenerative changes in the collagenous matrix, hypercellularity, hypervascularity, and a lack of inflammatory cells which has challenged the original misnomer "tendinitis".

The cause of de Quervain's disease is not established. Evidence regarding a possible relation with occupational risk factors is debated. A systematic review of potential risk factors discussed in the literature did not find any evidence of a causal relationship with occupational factors. However, researchers in France found personal and work-related factors were associated with de Quervain's disease in the working population; wrist bending and movements associated with the twisting or driving of screws were the most significant of the work-related factors. Proponents of the view that De Quervain syndrome is a repetitive strain injury consider postures where the thumb is held in abduction and extension to be predisposing factors. Workers who perform rapid repetitive activities involving pinching, grasping, pulling or pushing have been considered at increased risk. Specific activities that have been postulated as potential risk factors include intensive computer mouse use, trackball use, and typing, as well as some pastimes, including bowling, golf, fly-fishing, piano-playing, sewing, and knitting.

Women are affected more often than men. The syndrome commonly occurs during and after pregnancy. Contributory factors may include hormonal changes, fluid retention and—more debatably—lifting.

Supracondylar humerus fractures account for 55%-75% of all elbow fractures. They most commonly occur in children between ages 5–8, because remodeling of bone in this age group causes a decreased supracondylar anteroposterior diameter.

Enthesopathies may take the form of spondyloarthropathies (joint diseases of the spine) such as ankylosing spondylitis, plantar fasciitis, and Achilles tendinitis. Enthesopathy can occur at the elbow, wrist, carpus, hip, knee, ankle, tarsus, or heel bone, among other regions. Further examples include:

- Adhesive capsulitis of shoulder

- Rotator cuff syndrome of shoulder and allied disorders

- Periarthritis of shoulder

- Scapulohumeral fibrositis

- Synovitis of hand or wrist

- Periarthritis of wrist

- Gluteal tendinitis

- Iliac crest spur

- Psoas tendinitis

- Trochanteric tendinitis

Bursitis normally develops as a result either of a single injury to the elbow (for example, a hard blow to the tip of the elbow), or perhaps more commonly due to repeated minor injuries, such as repeated leaning on the point of the elbow on a hard surface. The chance of developing bursitis is higher if one's job or hobby involves a repetitive movement (for example, tennis, golf, or even repetitive computer work involving leaning on one's elbow). The likelihood of developing the condition is increased as one gets older.

As a reaction to injury, the lining of the bursa becomes inflamed. It then secretes a much greater than normal amount of fluid into the closed cavity of the bursa, from where it has nowhere to go. The bursa therefore inflates, producing a swelling over the proximal end of the ulna which is usually inflamed and tender.

Another possible cause of inflammation of the bursa is infection, which can usually (but not always) be traced to a crack or other lesion in the skin which allowed for bacteria of the normal skin flora to invade deeper layers of tissue.

Patellar tendinitis (patellar tendinopathy, also known as jumper's knee), is a relatively common cause of pain in the inferior patellar region in athletes. It is common with frequent jumping and studies have shown it may be associated with stiff ankle movement and ankle sprains.

Workers in certain fields are at risk of repetitive strains. Most occupational injuries are musculoskeletal disorders, and many of these are caused by cumulative trauma rather than a single event. Miners and poultry workers, for example, must make repeated motions which can cause tendon, muscular, and skeletal injuries.

In medicine, an enthesopathy refers to a disorder involving the attachment of a tendon or ligament to a bone. This site of attachment is known as the entheses.

If the condition is known to be inflammatory, it can more precisely be called an enthesitis.

Being an extremely rare disease, it is unknown as to what exactly causes Panner Disease. It is believed that the disease may be brought on by continuous overuse of the elbow and that puts pressure on the elbow and also strains the elbow in children during the period of rapid bone growth. The overuse of the elbow can be due to the involvement in sports such as baseball, handball, and gymnastics where these sports involve throwing or putting a lot of pressure on the joints. These repeated activities cause microtraumas and results in the affected elbow being swollen, irritated, and in pain. Panner Disease results when the blood supply to the capitellum is disrupted and therefore the cells within the growth plate of the capitellum die and it becomes flat due to the softening and collapsing of the surrounding bone. To prevent future instances of Panner Disease the child is instructed to cease all physical and sports activities that involve the use of the affected elbow until the symptoms are relieved.

De Quervain syndrome, is a tenosynovitis of the sheath or tunnel that surrounds two tendons that control movement of the thumb.