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.

A cubitus varus deformity is more cosmetic than limiting of any function, however internal rotation of the radius over the ulna may be limited due to the overgrowth of the humerus. This may be noticeable during an activity such as using a computer mouse.

The exact cause of Kienböck's is not known, though there are thought to be a number of factors predisposing a person to Kienböck's.

Recent studies have made a correlation between Kienböck's sufferers and Western European ancestry, but no definitive link can be positively confirmed.

The necrosis of the lunate bone can frequently be traced to a trauma to the wrist, like a compound fracture, which could cause the lunate's blood supply to be interrupted. Blood flows to the lunate through several arteries, each supplying a percentage. When one of these pathways is severed, the likelihood the patient will develop necrosis increases.

Despite a preponderance of evidence, no particular cause has been conclusively verified.

Data exists on the internet that most people suffering from Kienböck's are affected in their dominant hand, though about one-third of sufferers report the condition in their non-dominant hand. In very few cases have there been people that have acquired it in both wrists.

Kienböck's disease is classified as a "rare disorder," meaning that it affects fewer than 200,000 people in the U.S. population.

Many Kienböck's patients are frustrated by the lack of consensus among hand surgeons about optimal treatments for Kienböck's. No matter what the disease's stage of progression, there is no one best treatment, and the decision is often based partially, or even mostly, on incidental factors such as the patient's pain tolerance, the patient's desire to return to active use of the hand (such as in manual occupations), and the surgeon's level of expertise with different treatments.

Though, since each case of Kienböck's is different, the makeup of the wrist and arm bones are important factors which are individualized to each patient. Therefore, one surgery will never be able to solve all the problems associated with the disease. Thus, no consensus can be reached among surgeons.

A common cause is the supracondylar fracture of humerus. It can be corrected via a corrective osteotomy of the humerus and either internal or external fixation of the bone until union.

Leri-Weill dyschondrosteosis is a pseudoautosomal dominant disorder which occurs more frequently in females and is due to a mutation, deletion or duplication of the SHOX gene. The SHOX gene plays a particularly important role in the growth and maturation of bones in the arms and legs. The SHOX gene is located within band Xp22.3 of the pseudoautosomal region of the X chromosome, which escapes X-inactivation. Homozygous SHOX gene mutations result in Langer mesomelic dysplasia.

The cause of fibular hemimelia is unclear. Purportedly, there have been some incidents of genetic distribution in a family; however, this does not account for all cases. Maternal viral infections, embryonic trauma, teratogenic environmental exposures or vascular dysgenesis (failure of the embryo to form a satisfactory blood supply) between four and seven weeks gestation are considered possible causes.

In an experimental mouse model, change in the expression of a homeobox gene led to similar, but bilateral, fibular defects.

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).

It is a congenital subluxation or dislocation of the ulna's distal end, due to malformation of the bones. Sometimes, minor abnormalities of other bone structures, often caused by disease or injury, such as a fracture of the distal end of the radius with upward displacement of the distal fragment. The deformity varies in degree from a slight protrusion of the lower end of the ulna, to complete dislocation of the inferior radio-ulnar joint with marked radial deviation of the hand. Severe deformities are associated with congenital absence or hypoplasia of the radius.

The male:female rate of this disorder is 1:4. The incidence is unknown, and there is no described racial predominance. Even though Madelung's Deformity is considered a congenital disorder, symptoms sometimes aren't seen until adulthood. In most cases, symptoms find their onset during midchildhood. At this age, the relatively slower growth of the ulnar and palmar part of the radius, leads to an increasingly progressive deformity. Pain and deformity are the main symptoms patients present with. Typical clinical presentation consists of a short forearm, anterior-ulnar bow of the radius and a forward subluxation of the hand on the forearm. As mentioned before, the severity of the disorder varies greatly, which also leads to a spectrum of presentation.

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.

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.

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

Fibular hemimelia or longitudinal fibular deficiency is "the congenital absence of the fibula and it is the most common congenital absence of long bone of the extremities." It is the shortening of the fibula at birth, or the complete lack thereof. In humans, the disorder can be noted by ultrasound in utero to prepare for amputation after birth or complex bone lengthening surgery. The amputation usually takes place at six months with removal of portions of the legs to prepare them for prosthetic use. The other treatments which include repeated corrective osteotomies and leg-lengthening surgery (Ilizarov apparatus) are costly and associated with residual deformity.

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).

The incidence is less than 1/1.000.000. Fewer than 50 cases have been reported so far.

At the core of the disorder there is a homozygous or compound heterozygous mutation or deletion of the SHOX (Short Stature Homeobox), SHOXY (Short Stature Homeobox Y-linked) or PAR1 (where SHOX enhancer elements are located) genes, which is inherited in a pseudosomal recessive manner.

It is caused by mutations in the SHOX gene found in the pseudoautosomal region PAR1 of the X and Y chromosomes, at band Xp22.33 or Yp11.32.

SHOX gene deletions have been identified as the major cause of Leri–Weill syndrome.

Leri–Weill dyschondrosteosis is characterized by mesomelic short stature, with bowing of the radius more so than the ulna in the forearms and bowing of the tibia while sparing the fibula.

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.

In most cases persisting after childhood, there is little or no effect on the ability to walk. Due to uneven stress and wear on the knees, however, even milder manifestations can see an accelerated onset of arthritis.

Léri–Weill dyschondrosteosis or LWD is a rare pseudoautosomal dominant genetic disorder which results in dwarfism with short forearms and legs (mesomelic dwarfism) and a bayonet-like deformity of the forearms (Madelung's deformity).

Kienböck's disease is a disorder of the wrist. It is named for Dr. Robert Kienböck, a radiologist in Vienna, Austria who described osteomalacia of the lunate in 1910.

It is breakdown of the lunate bone, a carpal bone in the wrist that articulates with the radius in the forearm. Specifically, Kienböck's disease is another name for avascular necrosis (death and fracture of bone tissue due to interruption of blood supply) with fragmentation and collapse of the lunate. This has classically been attributed to arterial disruption, but may also occur after events that produce venous congestion with elevated interosseous pressure.

Classification of radial dysplasia is practised through different models. Some only include the different deformities or absences of the radius, where others also include anomalies of the thumb and carpal bones. The Bayne and Klug classification discriminates four different types of radial dysplasia. A fifth type was added by Goldfarb et al. describing a radial dysplasia with participation of the humerus. In this classification only anomalies of the radius and the humerus are taken in consideration. James and colleagues expanded this classification by including deficiencies of the carpal bones with a normal distal radius length as type 0 and isolated thumb anomalies as type N.

Type N: Isolated thumb anomaly

Type 0: Deficiency of the carpal bones

Type I: Short distal radius

Type II: Hypoplastic radius in miniature

Type III: Absent distal radius

Type IV: Complete absent radius

Type V: Complete absent radius and manifestations in the proximal humerus

The term absent radius can refer to the last 3 types.

Several studies have reported that life expectancy appears to be normal for people with CCD.

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.

If a child is sickly, either with rickets or any other ailment that prevents ossification of the bones, or is improperly fed, the bowed condition may persist. Thus the chief cause of this deformity is rickets. Skeletal problems, infection, and tumors can also affect the growth of the leg, sometimes giving rise to a one-sided bow-leggedness. The remaining causes are occupational, especially among jockeys, and from physical trauma, the condition being very likely to supervene after accidents involving the condyles of the femur.