Some studies suggest a hormonal link. Specifically, the hormone relaxin has been indicated.

A genetic factor is indicated since the trait runs in families and there is an increased occurrence in some ethnic populations (e.g., Native Americans, Lapps / Sami people). A locus has been described on chromosome 13. Beukes familial dysplasia, on the other hand, was found to map to an 11-cM region on chromosome 4q35, with nonpenetrant carriers not affected.

Hip dysplasia is considered to be a multifactorial condition. That means that several factors are involved in causing the condition to manifest.

The cause of this condition is unknown; however, some factors of congenital hip dislocation are through heredity and racial background. It is also thought that the higher rates in some ethnic groups (such as some Native American groups) is due to the practice swaddling of infants, which is known to be a potential risk factor for developing dysplasia. It also has a low risk in African Americans and southern Chinese.

The cause of PFFD is uncertain. Two hypotheses have been advanced. The theory of sclerotome subtraction posits injury to neural crest cells that are the precursors to sensory nerves at the level of L4 and L5. Histologic studies of a fetus with unilateral PFFD have prompted an alternative hypothesis that PFFD is caused by a defect in maturation of chondrocytes (cartilage cells) at the growth plate. In either hypothesis, the agent causing the injury is usually not known. Thalidomide is known to cause PFFD when the mother is exposed to it in the fifth or sixth week of pregnancy, and it is speculated that exposure to other toxins during pregnancy may also be a cause. Other etiologies that have been suggested, but not proven, include anoxia, ischemia, radiation, infection, hormones, and mechanical force. PFFD occurs sporadically, and does not appear to be hereditary.

In general, SCFE is caused by increased force applied across the epiphysis, or a decrease in the resistance within the physis to shearing. No single cause accounts for SCFEs, as several factors play a role in the development of a SCFE, particularly mechanical and endocrine (hormone-related) factors. Mechanical risk factors include obesity, coxa profunda, femoral or acetabular retroversion. Obesity is the most significant risk factor. In 65 percent of cases of SCFE, the person is over the 95th percentile for weight. Common misconception is heredity. Majority of cause is due to being overweight. Endocrine diseases also contribute, such as hypothyroidism, hypopituitarism, and renal osteodystrophy.

SCFE affects approximately 1-10 per 100,000 children. The incidence varies by geographic location, season of the year, and ethnicity. In eastern Japan, the incidence is 0.2 per 100,000 and in the northeastern U.S. it is about 10 per 100,000. Africans and Polynesians have higher rates of SCFE.

SCFEs are most common in adolescents 11–15 years of age, and affects boys more frequently than girls (male 2:1 female). It is strongly linked to obesity, and weight loss may decrease the risk. Other risk factors include: family history, endocrine disorders, radiation / chemotherapy, and mild trauma.

The left hip is more often affected than the right. Over half of cases may have involvement on both sides (bilateral).

There are typically four classes (or "types") of PFFD, ranging from class A to class D, as detailed by Aitken.

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.

Colles fractures occur in all age groups, although certain patterns follow an age distribution.

- In the elderly, because of the weaker cortex, the fracture is more often extra-articular.

- Younger individuals tend to require a higher energy force to cause the fracture and tend to have more complex intra-articular fractures. In children with open epiphyses, an equivalent fracture is the "epiphyseal slip", as can be seen in other joints, such as a slipped capital femoral epiphysis in the hip. This is a Salter I or II fracture with the deforming forces directed through the weaker epiphyseal plate.

- More common in women because of post-menopausal osteoporosis.

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.

Accidental or deliberate physical trauma may result in either a fracture, muscle bruising, or a contusion. It is the leading cause of a limp. Deliberate abuse is important to consider.

Radial dysplasia, also known as radial club hand or radial longitudinal deficiency, is a congenital difference occurring in a longitudinal direction resulting in radial deviation of the wrist and shortening of the forearm. It can occur in different ways, from a minor anomaly to complete absence of the radius, radial side of the carpal bones and thumb. Hypoplasia of the distal humerus may be present as well and can lead to stiffnes of the elbow. Radial deviation of the wrist is caused by lack of support to the carpus, radial deviation may be reinforced if forearm muscles are functioning poorly or have abnormal insertions. Although radial longitudinal deficiency is often bilateral, the extent of involvement is most often asymmetric.

The incidence is between 1:30,000 and 1:100,000 and it is more often a sporadic mutation rather than an inherited condition. In case of an inherited condition, several syndromes are known for an association with radial dysplasia, such as the cardiovascular Holt-Oram syndrome, the gastrointestinal VATER syndrome and the hematologic Fanconi anemia and TAR syndrome. Other possible causes are an injury to the apical ectodermal ridge during upper limb development, intrauterine compression, or maternal drug use (thalidomide).

Coxa vara is a deformity of the hip, whereby the angle between the head and the shaft of the femur is reduced to less than 120 degrees. This results in the leg being shortened, and the development of a limp. It is commonly caused by injury, such as a fracture. It can also occur when the bone tissue in the neck of the femur is softer than normal, causing it to bend under the weight of the body. This may either be congenital or the result of a bone disorder. The most common cause of coxa vara is either congenital or developmental. Other common causes include metabolic bone diseases (e.g. Paget's disease of bone), post-Perthes deformity, osteomyelitis, and post traumatic (due to improper healing of a fracture between the greater and lesser trochanter). Shepherd's Crook deformity is a severe form of coxa vara where the proximal femur is severely deformed with a reduction in the neck shaft angle beyond 90 degrees. It is most commonly a sequela of osteogenesis imperfecta, Pagets disease, osteomyelitis, tumour and tumour-like conditions (e.g. fibrous dysplasia).

Coxa vara can happen in cleidocranial dysostosis.

Other infections that classically lead to a limp include Lyme disease (a bacterial infection spread by a deer tick) and osteomyelitis (an infection of the bone).

Presence at birth is extremely rare and associated with other congenital anomalies such as proximal femoral focal deficiency, fibular hemimelia or anomalies in other part of the body such as cleidocranial dyastosis. The femoral deformity is present in the subtrochantric area where the bone is bent. The cortices are thickened and may be associated with overlying skin dimples. External rotation of the femur with valgus deformity of knee may be noted. This condition does not resolve and requires surgical management. Surgical management includes valgus osteotomy to improve hip biomechanics and length and rotational osteotomy to correct retroversion and lengthening.

The ultimate cause for these conditions is unknown, but the most commonly cited cause factors are rapid growth, heredity, trauma (or overuse), anatomic conformation, and dietary imbalances; however, only anatomic conformation and heredity are well supported by scientific literature. The way that the disease is initiated has been debated. Although failure of chondrocyte differentiation, formation of a fragile cartilage, failure of blood supply to the growth cartilage, and bone necrosis all have been proposed as the starting point in the pathogenesis, recent literature strongly supports failure of blood supply to growth cartilage as most likely.

Tibial plateau fractures constitute 1% of all fractures. Peak age is 30–40 years old in men and 60-70 in women. Approximately half of the people who sustain a tibial plateau fracture are aged over 50 years old.

FAI has been speculated as a cause of premature hip osteoarthritis and is characterized by abnormal contact between the proximal femur and rim of the acetabulum (hip socket). In most cases, patients present with a deformity in the femoral head, or acetabulum, a poorly positioned femoral-acetabular junction, or any or all of the foregoing. A combination of certain factors may predispose to some form of FAI, predominantly, a marginal developmental hip abnormality together with environmental factors such as activities involving recurrent motion of the legs within a supraphysiologic range.

Three types of FAI are recognized. The first involves an excess of bone along the upper surface of the femoral head, known as a Cam deformity (abbreviation for camshaft which the shape of the femoral head and neck resembles). The second is due to an excess of growth of the upper lip of the acetabular cup and is known as a 'Pincer' deformity. Colloquially, these are referred to as 'Cam' and 'Pincer'. The third is a combination of the two, generally referred to as 'Mixed'. Studies have suggested that 'Cam' deformities are more common in the male, while 'Pincer' deformities are more common in females. However, the most common situation, approximately 70%, is a combination of both. A complicating issue is that some of the radiographic findings of FAI have also been described in asymptomatic subjects. Consequently, the true frequency of femoroacetabular impingement is currently under debate, but the ultimate result is increased friction between the acetabular cup and femoral head which may result in pain and loss or reduction of hip function.

Coxa valga is a deformity of the hip where the angle formed between the head and neck of the femur and its shaft is increased, usually above 135 degrees. It is caused by a slipped epiphysis of the femoral head.

The differential diagnosis includes neuromuscular disorders (i.e. cerebral palsy, spinal dysraphism, poliomyelitis), skeletal dysplasias, and juvenile idiopathic arthritis.

Femoral shaft fractures occur in a bimodal distribution, whereby they are most commonly seen in males age 15-24 (due to high energy trauma) and females aged 75 or older (pathologic fractures due to osteoporosis, low-energy falls).

Femur-fibula-ulna syndrome (FFU syndrome) or femur-fibula-ulna complex is a very rare syndrome characterized by abnormalities of the femur (thigh bone), fibula (calf bone) and the ulna (forearm bone). There have been suggestions that FFU complex may be the same as proximal femoral focal deficiency (PFFD) although authors are currently in disagreement over whether or not the disorders are in fact separate. The breadth of the abnormality and number of limbs involved is considered sporadic although upper limbs are more affected than lower limbs and right side malformation is more prevalent than the left. The condition was first noted by Lenz and Feldman in 1977.

Femoroacetabular Impingement (FAI), or hip impingement syndrome, may affect the hip joint in young and middle-aged adults and occurs when the ball shaped femoral head rubs abnormally or does not permit a normal range of motion in the acetabular socket. Damage can occur to the articular cartilage, or labral cartilage (soft tissue bumper of the socket), or both. Treatment options range from conservative to arthroscopic to open surgery.

In the US, the annual incidence of stress fractures in athletes and military recruits ranges from 5% to 30%, depending on the sport and other risk factors. Women and highly active individuals are also at a higher risk. The incidence probably also increases with age due to age-related reductions in bone mass density (BMD). Children may also be at risk because their bones have yet to reach full density and strength. The female athlete triad also can put women at risk as disordered eating and osteoporosis can cause the bones to be severely weakened.

Humerus fractures are among the most common of fractures. Proximal fractures make up 5% of all fractures and 25% of humerus fractures, middle fractures about 60% of humerus fractures (12% of all fractures), and distal fractures the remainder. Among proximal fractures, 80% are one-part, 10% are two-part, and the remaining 10% are three- and four-part. The most common location of proximal fractures is at the surgical neck of the humerus. Incidence of proximal fractures increases with age, with about 75% of cases occurring among people over the age of 60. In this age group, about three times as many women than men experience a proximal fracture. Middle fractures are also common among the elderly, but they frequently occur among physically active young adult men who experience physical trauma to the humerus. Distal fractures are rare among adults, occurring primarily in children who experience physical trauma to the elbow region.

In most cases, patients are discharged from an emergency department with pain medicine and a cast or sling. These fractures are typically minor and heal naturally over the course of a few weeks. Fractures of the proximal region, especially among elderly patients, may limit future shoulder activity. Severe fractures are usually resolved with surgical intervention, followed by a period of healing using a cast or sling. Severe fractures often cause long-term loss of physical ability. Complications in the recovery process of severe fractures include osteonecrosis, malunion or nonunion of the fracture, stiffness, and rotator cuff dysfunction, which require additional intervention in order for the patient to fully recover.

A Colles' fracture is a type of fracture of the distal forearm in which the broken end of the radius is bent backwards. Symptoms may include pain, swelling, deformity, and bruising. Complications may include damage to the median nerve.

It is typically occurs as a result of a fall on an outstretched hand. Risk factors include osteoporosis. The diagnosis may be confirmed with X-rays. The tip of the ulna may also be broken.

Treatment may include casting or surgery. Reduction and casting is possible in the majority of cases in people over the age of 50. Pain management can be achieved during the reduction with procedural sedation and analgesia or a hematoma block. A year or two may be required for healing to occur.

About 15% of people have a Colles' fracture at some point in time. They occur more commonly in young adults and older people. Women are more often affected than men. The fracture is named after Abraham Colles who described it in 1814.