Women in sports such as association football, basketball, and tennis are significantly more prone to ACL injuries than men. The discrepancy has been attributed to gender differences in anatomy, general muscular strength, reaction time of muscle contraction and coordination, and training techniques.

Gender differences in ACL injury rates become evident when specific sports are compared. A review of NCAA data has found relative rates of injury per 1000 athlete exposures as follows:

- Men's basketball 0.07, women's basketball 0.23

- Men's lacrosse 0.12, women's lacrosse 0.17

- Men's football 0.09, women's football 0.28

The highest rate of ACL injury in women occurred in gymnastics, with a rate of injury per 1000 athlete exposures of 0.33

Of the four sports with the highest ACL injury rates, three were women's – gymnastics, basketball and soccer.

According to recent studies, female athletes are two to eight times more likely to strain their anterior cruciate ligament (ACL) in sports that involve cutting and jumping as compared to men who play the same particular sports (soccer, basketball, and volleyball). Differences between males and females identified as potential causes are the active muscular protection of the knee joint, the greater Q angle putting more medial torque on the knee joint, relative ligament laxity caused by differences in hormonal activity from estrogen and relaxin, intercondylar notch dimensions, and muscular strength.

Rate in the United States have been estimated to occur among an at-risk population of 1,774,210,081 people each year. Incidence rates published in the American Journal of Sports Medicine for ages 10–17 were found to be about 29 per 100,000 persons per year, while the adult population average for this type of injury ranged between 5.8 and 7.0 per 100,000 persons per year. The highest rates of patellar dislocation were found in the youngest age groups, while the rates declined with increasing ages. Females are more susceptible to patellar dislocation. Race is a significant factor for this injury, where Hispanics, African-Americans and Caucasians had slightly higher rates of patellar dislocation due to the types of athletic activity involved in: basketball (18.2%), soccer (6.9%), and football (6.9%), according to Brian Waterman.

Lateral Patellar dislocation is common among the child population. Some studies suggest that the annual patellar dislocation rate in children is 43/100,000. The treatment of the skeletally immature is controversial due to the fact that they are so young and are still growing. Surgery is recommended by some experts in order to repair the medial structures early, while others recommend treating it non operatively with physical therapy. If re-dislocation occurs then reconstruction of the medial patellofemoral ligament (MPFL) is the recommended surgical option.

Isolated and combined posterolateral knee injuries are difficult to accurately diagnose in patients presenting with acute knee injuries. The incidence of isolated posterolateral corner injuries has been reported to be between 13% and 28%. Most PLC injuries accompany an ACL or PCL tear, and can contribute to ACL or PCL reconstruction graft failure if not recognized and treated. A study by LaPrade "et al." in 2007 showed the incidence of posterolateral knee injuries in patients presenting with acute knee injuries and hemarthrosis (blood in the knee joint) was 9.1%.

High school athletes are at increased risk for ACL tears when compared to non-athletes. This risk increases with certain types of sports. Among high school girls, the sport with the highest risk of ACL tear is soccer, followed by basketball and lacrosse. The highest risk sport for boys was basketball, followed by lacrosse and soccer. Children and young athletes may benefit from early surgical reconstruction after ACL injury. Young athletes who have early surgical reconstruction of their torn ACL are more likely to return to their previous level of athletic ability when compared to those who underwent delayed surgery or nonoperative treatment. They are also less likely to experience instability in their knee if they undergo early surgery.

Hip dysplasia may be caused by a femur that does not fit correctly into the pelvic socket, or poorly developed muscles in the pelvic area. Large and giant breeds are most susceptible to hip dysplasia (possibly due to the body mass index (BMI) of the individual animal, though, many other breeds can suffer from it. The Orthopedic Foundation for Animals maintains a list of top 100 breeds affected.

To reduce pain, the animal will typically reduce its movement of that hip. This may be visible as "bunny hopping", where both legs move together, or less dynamic movement (running, jumping), or stiffness. Since the hip cannot move fully, the body compensates by adapting its use of the spine, often causing spinal, stifle (a dog's knee joint), or soft tissue problems to arise.

The causes of hip dysplasia are considered heritable, but new research conclusively suggests that environment also plays a role. To what degree the causality is genetic and what portion environmental is a topic of current debate. Neutering a dog, especially before the dog has reached an age of full developmental maturity, has been proven to almost double the chance he or she will develop hip dysplasia versus intact dogs or dogs that were neutered after reaching adulthood Other environmental influences include overweight condition, injury at a young age, overexertion on the hip joint at a young age, ligament tear at a young age, repetitive motion on forming joint (i.e. jogging with puppy under the age of 1 year). As current studies progress, greater information may help provide procedures to effectively reduce the occurrence of this condition.

The problem almost always appears by the time the dog is 18 months old. The defect can be anywhere from mild to severely crippling, and can eventually cause severe osteoarthritis.

It is most common in medium-large pure bred dogs, such as Newfoundlands, German Shepherd Dogs, retrievers (such as Labradors, Tollers, or Goldens), rottweilers and Mastiff, but also occurs in some smaller breeds such as spaniels and pugs.

Children younger than 6 have the best prognosis, since they have time for the dead bone to revascularize and remodel, with a good chance that the femoral head will recover and remain spherical after resolution of the disease. Children who have been diagnosed with Perthes' disease after the age of 10 are at a very high risk of developing osteoarthritis and coxa magna. When an LCP disease diagnosis occurs after age 8, a better outcome results with surgery rather than nonoperative treatments. Shape of femoral head at the time when Legg-Calve Perthes disease heals is the most important determinant of risk for degenerative arthritis; hence, the shape of femoral head and congruence of hip are most useful outcome measures.

Perthes' disease is one of the most common hip disorders in young children, occurring in roughly 5.5 of 100,000 children per year. The lifetime risk of a child developing the disease is about one per 1,200 individuals. Boys are affected about three to five times more often than girls. New cases of Perthes' disease rarely occur after age 14 years (if diagnosed after 14 years of age, then it is usually old disease from early in childhood or avascular necrosis from an alternative cause).

White northern Europeans appear to be affected more frequently than other races, though a paucity of reliable epidemiology exists in the Southern Hemisphere. Children of sufferers of the disease themselves may have a very slightly increased risk, though it is unclear if this is because of a genetic predisposition, or a shared environmental factor. It is most commonly seen in persons aged three to 12 years, with a median of six years of age. The UK incidence rates show an intriguing pattern with low incidence rates in London, and a progressive increase in disease in more northerly areas (maximal in Scotland). Some evidence suggests, at least in developed countries, more socioeconomically deprived communities have a greater risk of disease (a similar trend to diseases such as adult heart disease), though the reason for this remains unknown. One possible explanation that has been considered is tobacco smoke exposure, though this is significantly confounded by the strong socioeconomic gradient common to both smoking and Perthes' disease. Dietary factors of the child, and of the mother during pregnancy, are of interest to the research groups.

Dislocation of the hip is a common injury to the hip joint. Dislocation occurs when the ball–shaped head of the femur comes out of the cup–shaped acetabulum set in the pelvis.

Dislocations may be developmental or due to acute trauma. The emphasis of this article is on acute dislocation. For developmental dislocation, see hip dysplasia.

Acute traumatic hip dislocations are severe injuries. These dislocations typically occur in 16- to 40-year-olds involved in high energy trauma like motor vehicle accidents.

16-40 year-old males are responsible for the majority of hip dislocations. These hip dislocations are typically posterior, and a direct result of motor vehicle traffic collisions.

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.

Future research into posterolateral injuries will focus on both the treatment and diagnosis of these types of injuries to improve PLC injury outcomes. Studies are needed to correlate injury patterns and mechanisms with clinical measures of knee instability and laxity.

In dogs, hip dysplasia is an abnormal formation of the hip socket that, in its more severe form, can eventually cause crippling lameness and painful arthritis of the joints. It is a genetic (polygenic) trait that is affected by environmental factors. It is common in many dog breeds, particularly the larger breeds, and is the most common single cause of arthritis of the hips.

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.

A patellar dislocation is a knee injury in which the patella (kneecap) slips out of its normal position. Often the knee is partly bent, painful and swollen. The patella is also often felt and seen out of place. Complications may include a patella fracture or arthritis.

A patellar dislocation typically occurs when the knee is straight and the lower leg is bent outwards when twisting. Occasionally it occurs when the knee is bent and the patella is hit. Commonly associated sports include soccer, gymnastics, and ice hockey. Dislocations nearly always occur away from the midline. Diagnosis is typically based on symptoms and supported by X-rays.

Reduction is generally done by pushing the patella towards the midline while straightening the knee. After reduction the leg is generally splinted in a straight position for a few weeks. This is then followed by physical therapy. Surgery after a first dislocation is generally of unclear benefit. Surgery may be indicated in those who have broken off a piece of bone within the joint or in which the patella has dislocated multiple times.

Patellar dislocations occur in about 6 per 100,000 people per year. They make up about 2% of knee injuries. It is most common in those 10 to 17 years years old. Rates in males and females are similar. Recurrence after an initial dislocation occurs in about 30% of people.

The following factors may be involved in causing this deformity:

- Inherent laxity of the knee ligaments

- Weakness of biceps femoris muscle

- Instability of the knee joint due to ligaments and joint capsule injuries

- Inappropriate alignment of the tibia and femur

- Malunion of the bones around the knee

- Weakness in the hip extensor muscles

- Gastrocnemius muscle weakness (in standing position)

- Upper motor neuron lesion (for example, hemiplegia as the result of a cerebrovascular accident)

- Lower motor neuron lesion (for example, in post-polio syndrome)

- Deficit in joint proprioception

- Lower limb length discrepancy

- Congenital genu recurvatum

- Cerebral palsy

- Multiple sclerosis

- Muscular dystrophy

- Limited dorsiflexion (plantar flexion contracture)

- Popliteus muscle weakness

- Connective tissue disorders. In these disorders, there are excessive joint mobility (joint hypermobility) problems. These disorders include:

- Marfan syndrome

- Ehlers-Danlos syndrome

- Benign hypermobile joint syndrome

- Osteogenesis imperfecta disease

The most important factors of knee stability include:

- Ligaments of the knee: The knee joint is stabilized by four main ligaments:

- Anterior cruciate ligament (ACL). The ACL has an important role in stabilization of knee extension movement by preventing the knee from hyperextending.

- Posterior cruciate ligament (PCL)

- Medial collateral ligament (MCL)

- Lateral collateral ligament (LCL)

- Joint capsule or articular capsule (especially posterior knee capsule)

- Quadriceps femoris muscle

- Appropriate alignment of the femur and tibia (especially in knee extension position )

A Soft tissue injury (STI) is the damage of muscles, ligaments and tendons throughout the body. Common soft tissue injuries usually occur from a sprain, strain, a one off blow resulting in a contusion or overuse of a particular part of the body. Soft tissue injuries can result in pain, swelling, bruising and loss of function (Lovering, 2008)

An overuse injury occurs when a certain activity is repeated frequently, and the body doesn't have enough time to recover in between occurrences. Some examples include bursitis and tendinitis.

Medial knee injuries are those to the medial side – the inside of the knee – are the most common. The medial ligament complex of the knee is composed of the superficial medial collateral ligament (sMCL), deep medial collateral ligament (dMCL), and the posterior oblique ligament (POL). These ligaments have also been called the medial collateral ligament (MCL), tibial collateral ligament, mid-third capsular ligament, and oblique fibers of the sMCL, respectively. This complex is the major stabilizer of the medial knee. Injuries to the medial side of the knee are most commonly isolated to these ligaments. A thorough understanding of the anatomy and function of the medial knee structures, along with a detailed history and physical exam, are imperative to diagnosing and treating these injuries.

Future research with regard to medial knee injuries should evaluate clinical outcomes between different reconstruction techniques. Determining the advantages and disadvantages of these techniques would also be beneficial for optimizing treatment.

Fairbank's disease or multiple epiphyseal dysplasia (MED) is a rare genetic disorder (dominant form: 1 in 10,000 births) that affects the growing ends of bones. Long bones normally elongate by expansion of cartilage in the growth plate (epiphyseal plate) near their ends. As it expands outward from the growth plate, the cartilage mineralizes and hardens to become bone (ossification). In MED, this process is defective.

Multiple epiphyseal dysplasia (MED) encompasses a spectrum of skeletal disorders, most of which are inherited in an autosomal dominant form. However, there is an autosomal recessive form.

Associated genes include COL9A1, COL9A2, COL9A3, COMP, and MATN3.

Types include:

Possible causes that lead to the condition of Lumbar hyperlordosis are the following:

- Spines – Natural factors of how spines are formed greatly increase certain individuals' likelihood to experience a strain or sprain in their back or neck. Factors such as having more lumbar vertebrae allowing for too much flexibility, and then in cases of less lumbar the individual not reaching their necessity for flexibility and then pushing their bodies to injury.

- Legs – Another odd body formation is when an individual has a leg shorter than the other, which can be immediate cause for imbalance of hips then putting strain on the posture of the back which an individual has to adjust into vulnerable positions to meet aesthetic appearances. This can lead to permanent damage in the back. Genu recurvatum (sway back knees) is also a factor that forces a dancer to adjust into unstable postures.

- Hips – Common problems in the hips are tight hip flexors, which causes for poor lifting posture, hip flexion contracture, which means the lack of postural awareness, and thoracic hyperkyphosis, which causes the individual to compensate for limited hip turn out (which is essential to dances such as ballet). Weak psoas (short for iliopsoas-muscle that controls the hip flexor) force the dancer to lift from strength of their back instead of from the hip when lifting their leg into arabesque or attitude. This causes great stress and risk of injury, especially because the dancer will have to compensate to obtain the positions required.

- Muscles – One of the greatest contributors is uneven muscles. Because all muscles have a muscle that works in opposition to it, it is imperative that to keep all muscles protected, the opposite muscle is not stronger than the muscle at risk. In the situation of lumbar lordosis, abdominal muscles are weaker than the muscles in the lumbar spine and the hamstring muscles. The muscular imbalance results in pulling down the pelvis in the front of the body, creating the swayback in the spine.

- Growth spurt – Younger dancers are more at risk for development of lumbar hyperlordosis because the lumbar fascia and hamstrings tighten when a child starts to experience a growth spurt into adolescence.

Technical factors

- Improper lifts – When male dancers are performing dance lifts with another dancer they are extremely prone to lift in the incorrect posture, pushing their arms up to lift the other dancer, while letting their core and spine curve which is easy to then hyperlordosis in a dancer's back.

- Overuse – Over 45% of anatomical sites of injury in dancers are in the lower back. This can be attributed to the strains of repetitive dance training may lead to minor trauma. If the damaged site is not given time to heal the damage of the injury will increase. Abrupt increases in dance intensity or sudden changes in dance choreography do not allow the body to adapt to the new stresses. New styles of dance, returning to dance, or increasing dance time by a great deal will result in exhaustion of the body.

Lordosis refers to the normal inward "lordotic" curvature of the lumbar and cervical regions of the human spine. The normal outward (convex) curvature in the thoracic and sacral regions is termed kyphosis or "kyphotic". The term comes from the Greek lordōsis, from "lordos" ("bent backward").

Lordosis in the human spine makes it easier for humans to bring the bulk of their mass over the pelvis. This allows for a much more efficient walking gait than that of other primates, whose inflexible spines cause them to resort to an inefficient forward leaning "bent-knee, bent-waist" gait. As such, lordosis in the human spine is considered one of the primary physiological adaptations of the human skeleton that allows for human gait to be as energetically efficient as it is.

Lower spine disorders occur when lumbar lordosis is excessive (lumbar hyperlordosis), minimal, or reversed into lumbar kyphosis. Lumbar hyperlordosis is commonly called hollow back or saddle back (after a similar condition that affects some horses). These conditions are usually a result of poor posture and can often be reversed by learning correct posture and using appropriate exercises.