Specific populations at high risk of primary PFPS include runners, bicyclists, basketball players, young athletes and females.

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.

The prevalence of Achilles tendinitis fluctuates greatly among different ages and groups of people. However, Achilles tendinitis is most commonly found in individuals aged 30–40. A study was conducted in 1981 on recreational and competitive runners and what type of injury they were most likely to suffer from. Out of the 232 runners, 25 (11%) complained that their Achilles bothered them.

A study conducted in the city of Oulu found that a peak incidence of 18 injured Achilles occurred in 1994 and was highest in the male group aged 30–39. The study also found that 90% of the injuries occurred while playing a sport.

Risk factors include participating in a sport or activity that involves running, jumping, bounding, and change of speed. Although Achilles tendinitis is mainly diagnosed in runners, it does occur in basketball, volleyball, dancing, gymnastics and other athletic activities. Other risk factors include gender, age, improper stretching, overuse, and conditions which the individual may be born with. Congenital conditions occur when an individual’s legs rotate abnormally, which in turn causes the lower extremities to overstretch and contract; this puts stress on the Achilles tendon and will eventually cause Achilles tendinitis.

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.

A rotator cuff tear can be caused by the weakening of the rotator cuff tendons. This weakening can be caused by age or how often the rotator cuff is used. Adults over the age of 60 are more susceptible to a rotator cuff tear. According to a study in the Journal of Orthopaedic Surgery and Traumatology the frequency of rotator cuff tears can increase with age. The study shows the participants that were the ages of 70–90 years old had a rate of rotator cuff tears that were 1 to 5. The participants who were 90+ years old the frequency of a rotator cuff tear jumped to 1 to 3. This study shows that with an increase in age there is also an increase in the probability of a rotator cuff tear.

Identified risk factors for plantar fasciitis include excessive running, standing on hard surfaces for prolonged periods of time, high arches of the feet, the presence of a leg length inequality, and flat feet. The tendency of flat feet to excessively roll inward during walking or running makes them more susceptible to plantar fasciitis. Obesity is seen in 70% of individuals who present with plantar fasciitis and is an independent risk factor.

Studies have suggested a strong association exists between an increased body mass index and the development of plantar fasciitis in the non-athletic population; this association between weight and plantar fasciitis has not been observed in the athletic population. Achilles tendon tightness and inappropriate footwear have also been identified as significant risk factors.

The cause of snapping hip syndrome is not well understood, and confusion exists within the medical community regarding causation. Athletes appear to be at an enhanced risk for snapping hip syndrome due to repetitive and physically demanding movements.

In athletes such as ballet dancers, gymnasts, horse riders, track and field athletes and soccer players, military training, or any vigorous exerciser, repeated hip flexion leads to injury. In excessive weightlifting or running, the cause is usually attributed to extreme thickening of the tendons in the hip region. Snapping hip syndrome most often occurs in people who are 15 to 40 years old.

Plantar fasciitis is the most common type of plantar fascia injury and is the most common reason for heel pain, responsible for 80% of cases. The condition tends to occur more often in women, military recruits, older athletes, the obese, and young male athletes.

Plantar fasciitis is estimated to affect 1 in 10 people at some point during their lifetime and most commonly affects people between 40–60 years of age. In the United States alone, more than two million people receive treatment for plantar fasciitis. The cost of treating plantar fasciitis in the United States is estimated to be $284 million each year.

Extra-articular snapping hip syndrome is commonly associated with leg length difference (usually the long side is symptomatic), tightness in the iliotibial band (ITB) on the involved side, weakness in hip abductors and external rotators, poor lumbopelvic stability and abnormal foot mechanics (overpronation). Popping occurs when the thickened posterior aspect of the ITB or the anterior gluteus maximus rubs over the greater trochanter as the hip is extended.

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%.

While people with rotator cuff tears may not have any noticeable symptoms, studies have shown that over time 40% will have enlargement of the tear over a five-year period. Of those whose tears enlarge, 20% have no symptoms while 80% eventually develop symptoms.

There is no irrefutable evidence that rotator cuff surgery benefits patients more than non-surgical management and a percentage of patients never regain full range of motion after surgery.

Epidemiological studies strongly support a relationship between age and cuff tear prevalence. In a recent study the frequency of such tears increased from 13% in the youngest group (aged 50–59 y) to 20% (aged 60–69 y), 31% (aged 70–79 y), and 51% in the oldest group (aged 80–89 y). This high rate of tear prevalence in asymptomatic individuals suggests that rotator cuff tears could be considered a "normal" process of aging rather than a result of an apparent pathological process.

Plantar fasciitis is a common cause of calcaneal spurs. To quote Edward Kwame Agyekum, "When stress is put on the plantar fascia ligament, it does not cause only plantar fasciitis, but cause[s] a heel spur... where the plantar fascia attaches to the heel bone. Generally, a calcaneal spur develops when proper care is not given to the foot and heels. People who are obese, have flat feet, or who often wear high-heeled shoes are most susceptible to heel spurs.

Development of tendinitis depends on the type, frequency and severity of exercise or use; for example, rock climbers tend to develop tendinitis in their fingers, swimmers in their shoulders. Achilles tendinitis is a common injury, particularly in sports that involve lunging and jumping. It is also a known side effect of fluoroquinolone antibiotics such as ciprofloxacin, as are other types of tendinitis.

Swelling in a region of micro-damage or partial tear can be detected visually or by touch. Increased water content and disorganized collagen matrix in tendon lesions may be detected by ultrasonography or magnetic resonance imaging.

Achilles tendinitis is thought to have physiological, mechanical, or extrinsic (i.e. footwear or training) causes. Physiologically, the Achilles tendon is subject to poor blood supply through the synovial sheaths that surround it. This lack of blood supply can lead to the degradation of collagen fibers and inflammation. Tightness in the calf muscles has also been known to be involved in the onset of Achilles tendinitis.

During the loading phase of the running and walking cycle, the ankle and foot naturally pronate and supinate by approximately 5 degrees. Excessive pronation of the foot (over 5 degrees) in the subtalar joint is a type of mechanical mechanism that can lead to tendinitis.

An overuse injury refers to repeated stress and strain, which is likely the case in endurance runners. Overuse can simply mean an increase in running, jumping or plyometric exercise intensity too soon. Another consideration would be the use of improper or worn-down footwear, which lack the necessary support to maintain the foot in the natural/normal pronation.

In most patients with PFPS an examination of their history will highlight a precipitating event that caused the injury. Changes in activity patterns such as excessive increases in running mileage, repetitions such as running up steps and the addition of strength exercises that affect the patellofemoral joint are commonly associated with symptom onset. Excessively worn or poorly fitted footwear may be a contributing factor. To prevent recurrence the causal behaviour should be identified and managed correctly.

The medical cause of PFPS is thought to be increased pressure on the patellofemoral joint. There are several theorized mechanisms relating to how this increased pressure occurs:

- Increased levels of physical activity

- Malalignment of the patella as it moves through the femoral groove

- Quadriceps muscle imbalance

- Tight anatomical structures, e.g. retinaculum or iliotibial band.

The cause of pain and dysfunction often results from either abnormal forces (e.g. increased pull of the lateral quadriceps retinaculum with acute or chronic lateral PF subluxation/dislocation) or prolonged repetitive compressive or shearing forces (running or jumping) on the PF joint. The result is synovial irritation and inflammation and subchondral bony changes in the distal femur or patella known as "bone bruises". Secondary causes of PF Syndrome are fractures, internal knee derangement, osteoarthritis of the knee and bony tumors in or around the knee.

In 2010 national statistics was done by Agency for Healthcare Research and Quality for posterior cruciate ligaments injuries. They found that 463 patients were discharge for having some type of PCL injury. The 18- to 44-year-old age group was found to have the highest injuries reported (figure 1). One reason why this age group consists of the majority of injuries to the PCL is because people are still very active in sports at this age. Men were also reported having more injuries to the PCL (figure 3).

Bone mineral density decreases with increasing age. Osteoporotic bone loss can be prevented through an adequate intake of vitamin C and vitamin D, coupled with exercise and by being a non-smoker. A study by Cheng et al. in 1997, showed that greater bone density indicated less risk for fractures in the calcaneus.

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.

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.

The literature on the pathophysiology of bursitis describes inflammation as the primary cause of symptoms. Inflammatory bursitis is usually the result of repetitive injury to the bursa.

In the subacromial bursa, this generally occurs due to microtrauma to adjacent structures, particularly the supraspinatus tendon. The inflammatory process causes synovial cells to multiply, increasing collagen formation and fluid production within the bursa and reduction in the outside layer of lubrication (Ishii et al., 1997).

Less frequently observed causes of subacromial bursitis include hemorrhagic conditions, crystal deposition and infection.

Many causes have been proposed in the medical literature for subacromial impingement syndrome. The bursa facilitates the motion of the rotator cuff beneath the arch, any disturbance of the relationship of the subacromial structures can lead to impingement. These factors can be broadly classified as intrinsic such as tendon degeneration, rotator cuff muscle weakness and overuse. Extrinsic factors include bone spurs from the acromion or AC joint, shoulder instability and neurologic problems arising outside of the shoulder.

According to the posterior cruciate ligament injuries only account for 1.5 percent of all knee injuries (figure 2). If it is a single injury to the posterior cruciate ligament that requires surgery only accounted for 1.1 percent compared to all other cruciate surgeries but when there was multiple injuries to the knee the posterior cruciate ligament accounted for 1.2 percent of injuries.

A study containing 100 consecutive patients with a recent anterior cruciate ligament injury were examined with respect to type of sports activity that caused the injury. Of the 100 consecutive ACL injuries, there were also 53 medial collateral ligament injuries, 12 medial, 35 lateral and 11 bicompartmental meniscal lesions. 59/100 patients were injured during contact sports, 30/100 in downhill skiing and 11/100 in other recreational activities, traffic accidents or at work.

An associated medial collateral ligament tear was more common in skiing (22/30) than during contact sports (23/59), whereas a bicompartmental meniscal lesion was found more frequently in contact sports (9/59) than in skiing (0/30). Weightbearing was reported by 56/59 of the patients with contact sports injuries whereas 8/30 of those with skiing injuries. Non-weightbearing in the injury situation led to the same rate of MCL tears (18/28) as weightbearing (35/72) but significantly more intact menisci (19/28 vs 23/72). Thus, contact sports injuries were more often sustained during weightbearing, with a resultant joint compression of both femuro-tibial compartments as shown by the higher incidence of bicompartmental meniscal lesions. The classic "unhappy triad" was a rare finding (8/100) and Fridén T, Erlandsson T, Zätterström R, Lindstrand A, and Moritz U. suggest that this entity should be replaced by the "unhappy compression injury".

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

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.

Calcaneal fractures are often attributed to shearing stress adjoined with compressive forces combined with a rotary direction (Soeur, 1975). These forces are typically linked to injuries in which an individual falls from a height, involvement in an automobile accident, or muscular stress where the resulting forces can lead to the trauma of fracture. Overlooked aspects of what can lead to a calcaneal fracture are the roles of osteoporosis and diabetes.

Unfortunately, the prevention of falls and automobile accidents is limited and applies to unique circumstances that should be avoided. The risk of muscular stress fractures can be reduced through stretching and weight-bearing exercise, such as strength training. In addition, footwear can influence forces that may cause a calcaneal fracture and can prevent them as well. A 2012 study conducted by Salzler showed that the increasing trend toward minimalist footwear or running barefoot can lead to a variety of stress fractures including that of the calcaneus.

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.