If the diver has not been exposed to excessive depth and decompression and presents as DON, there may be a predisposition for the condition. Diving should be restricted to shallow depths. Divers who have suffered from DON are at increased risk of future fracture of a juxta-articular lesion during a dive, and may face complications with future joint replacements. Because of the young age of the population normally affected, little data is available regarding joint replacement complications.

There is the potential for worsening of DON for any diving where there might be a need for decompression, experimental or helium diving. Physically stressful diving should probably be restricted, both in sport diving and work diving due to the possibility of unnecessary stress to the joint. Any diving should be less than 40 feet/12 meters. These risks are affected by the degree of disability and by the type of lesion (juxta-articular or shaft).

Avascular necrosis usually affects people between 30 and 50 years of age; about 10,000 to 20,000 people develop avascular necrosis of the head of the femur in the US each year. When it occurs in children at the femoral head, it is known as Legg-Calvé-Perthes syndrome.

A variety of methods may be used to treat the most common being the total hip replacement (THR). However, THRs have a number of downsides including long recovery times and short life spans (of the hip joints). THRs are an effective means of treatment in the older population; however, in younger people they may wear out before the end of a person's life.

Other technicques such as metal on metal resurfacing may not be suitable in all cases of avascular necrosis; its suitability depends on how much damage has occurred to the femoral head. Bisphosphonates which reduces the rate of bone breakdown may prevent collapse (specifically of the hip) due to AVN.

Treatment is difficult, often requiring a joint replacement. Spontaneous improvement occasionally happens and some juxta-articular lesions do not progress to collapse. Other treatments include immobilization and osteotomy of the femur. Cancellous bone grafts are of little help.

The Orthopedic Foundation for Animals in the United States will grade elbow X-rays of dogs intended for breeding.

The goals of treatment are to decrease pain, reduce the loss of hip motion, and prevent or minimize permanent femoral head deformity so that the risk of developing a severe degenerative arthritis as adult can be reduced. Assessment by a pediatric orthopaedic surgeon is recommended to evaluate risks and treatment options. Younger children have a better prognosis than older children.

Treatment has historically centered on removing mechanical pressure from the joint until the disease has run its course. Options include traction (to separate the femur from the pelvis and reduce wear), braces (often for several months, with an average of 18 months) to restore range of motion, physiotherapy, and surgical intervention when necessary because of permanent joint damage. To maintain activities of daily living, custom orthotics may be used. Overnight traction may be used in lieu of walking devices or in combination. These devices internally rotate the femoral head and abduct the leg(s) at 45°. Orthoses can start as proximal as the lumbar spine, and extend the length of the limbs to the floor. Most functional bracing is achieved using a waist belt and thigh cuffs derived from the Scottish-Rite orthosis. These devices are typically prescribed by a physician and implemented by an orthotist. Clinical results of the Scottish Rite orthosis have not been good according to some studies, and its use has gone out of favor. Many children, especially those with the onset of the disease before age 6, need no intervention at all and are simply asked to refrain from contact sports or games which impact the hip. For older children (onset of Perthes after age 6), the best treatment option remains unclear. Current treatment options for older children over age 8 include prolonged periods without weight bearing, osteotomy (femoral, pelvic, or shelf), and the hip distraction method using an external fixator which relieves the hip from carrying the body's weight. This allows room for the top of the femur to regrow. The Perthes Association has a "library" of equipment which can be borrowed to assist with keeping life as normal as possible, newsletters, a helpline, and events for the families to help children and parents to feel less isolated.

While running and high-impact sports are not recommended during treatment for Perthes disease, children can remain active through a variety of other activities that limit mechanical stress on the hip joint. Swimming is highly recommended, as it allows exercise of the hip muscles with full range of motion while reducing the stress to a minimum. Cycling is another good option as it also keeps stress to a minimum. Physiotherapy generally involves a series of daily exercises, with weekly meetings with a physiotherapist to monitor progress. These exercises focus on improving and maintaining a full range of motion of the femur within the hip socket. Performing these exercises during the healing process is essential to ensure that the femur and hip socket have a perfectly smooth interface. This will minimize the long-term effects of the disease. Use of bisphosphonate such as zoledronate or ibandronate is currently being investigated, but definite recommendations are not yet available.

Perthes disease is self-limiting, but if the head of femur is left deformed, long-term problems can occur. Treatment is aimed at minimizing damage while the disease runs its course, not at 'curing' the disease. It is recommended not to use steroids or alcohol as these reduce oxygen in the blood which is needed in the joint. As sufferers age, problems in the knee and back can arise secondary to abnormal posture and stride adopted to protect the affected joint. The condition is also linked to arthritis of the hip, though this appears not to be an inevitable consequence. Hip replacements are relatively common as the already damaged hip suffers routine wear; this varies by individual, but generally is required any time after age 50.

In a recent comparative orthopedic study, a new bioscaffold having an embryonic-like structure has shown positive clinical outcomes in dogs with advanced, end stage osteoarthritis. The bioscaffold was implanted into intra-articular areas and reported up to 90-days of clinical improvement after a single implant. The bioscaffold has been shown to cause infiltrating cells to upregulate a variety of tissue repair factors including aggrecan, connective tissue growth factor, bone morphogenetic protein, transforming growth factors, and other tissue repair factors associated with osteoarthritis TR BioSurgical, LLC.

Legg–Calvé–Perthes disease (LCPD, also known as Perthes disease or Legg–Perthes disease) is a childhood hip disorder initiated by a disruption of blood flow to the head of the femur. Due to the lack of blood flow, the bone dies (osteonecrosis or avascular necrosis) and stops growing. Over time, healing occurs by new blood vessels infiltrating the dead bone and removing the necrotic bone which leads to a loss of bone mass and a weakening of the femoral head. The bone loss leads to some degree of collapse and deformity of the femoral head and sometimes secondary changes to the shape of the hip socket. It is also referred to as idiopathic avascular osteonecrosis of the capital femoral epiphysis of the femoral head since the cause of the interruption of the blood supply of the head of the femur in the hip joint is unknown.

The condition is most commonly found in children between the ages of 4 and 8, but it can occur in children between the ages of 2 and 15. The main long-term problem with this condition is that it can produce a permanent deformity of the femoral head, which increases the risk of developing osteoarthritis in adults. Perthes is a form of osteochondritis which only affects the hip, although other forms of osteochondritis can affect elbows, knees, ankles, and feet. Bilateral Perthes, which means both hips are affected, should always be investigated thoroughly to rule out multiple epiphyseal dysplasia.

By definition, a nonunion will not heal if left alone. Therefore the patient's symptoms will not be improved and the function of the limb will remain impaired. It will be painful to bear weight on it and it may be deformed or unstable. The prognosis of nonunion if treated depends on many factors including the age and general health of the patient, the time since the original injury, the number of previous surgeries, smoking history, the patient's ability to cooperate with the treatment. In the region of 80% of nonunions heal after the first operation. The success rate with subsequent surgeries is less.

First described by Preiser in 1910 in 5 patients, all with previous history of wrist trauma, and scaphoid fractures in 3 of them.

The choice of surgical versus non-surgical treatments for osteochondritis dissecans is controversial. Consequently, the type and extent of surgery necessary varies based on patient age, severity of the lesion, and personal bias of the treating surgeon—entailing an exhaustive list of suggested treatments. A variety of surgical options exist for the treatment of persistently symptomatic, intact, partially detached, and completely detached OCD lesions. Post-surgery reparative cartilage is inferior to healthy hyaline cartilage in glycosaminoglycan concentration, histological, and immunohistochemical appearance. As a result, surgery is often avoided if non-operative treatment is viable.

Treatment options include modified activity with or without weight bearing; immobilization; cryotherapy; anti-inflammatory medication; drilling of subchondral bone; microfracture; removal or reattachment of loose bodies; mosaicplasty and osteoarticular transfer system (OATS) procedures. The primary goals of treatment are:

1. Enhance the healing potential of subchondral bone;

2. Fix unstable fragments while maintaining joint congruity; and

3. Replace damaged bone and cartilage with implanted tissues or cells that can grow cartilage.

The articular cartilage's capacity for repair is limited: partial-thickness defects in the articular cartilage do not heal spontaneously, and injuries of the articular cartilage which fail to penetrate subchondral bone tend to lead to deterioration of the articular surface. As a result, surgery is often required in even moderate cases where the osteochondral fragment has not detached from the bone (Anderson Stage II, III).

Bone stimulation may be with either electromagnetic or ultrasound waves. Ultrasound stimulation has tentative evidence of supporting better healing in long bones that have not healed after three months. Evidence; from a Cochrane review however, does not show that ultrasound decreases rates of nonunion. Another review has, however, suggested it as an alternative to surgery.

Preiser disease, or (idiopathic) avascular necrosis of the scaphoid, is a rare condition where ischemia and necrosis of the scaphoid bone occurs without previous fracture. It is thought to be caused by repetitive microtrauma or side effects of drugs (e.g., steroids or chemotherapy) in conjunction with existing defective vascular supply to the proximal pole of the scaphoid. MRI coupled with CT and X-ray are the methods of choice for diagnosis.

Preiser's disease is initially treated by immobilising the wrist with a cast. However, in most cases the avascular scaphoid will start to collapse leading to degeneration within the wrist joints. This often requires surgical intervention to prevent the progression of arthris. Two commonly performed procedures are:

1. Proximal row carpectomy (PRC), which involves removing the first row of the carpal bones, i.e. the scaphoid, lunate and triquetrum. The wrist is immobilised in a cast for six weeks after the surgery and then physiotherapy is started.

2. Scaphoid excision and 4-corner fusion, which is a procedure consisting of the removal of the scaphoid and fixation of the remaining wrist bones with a plate (called a "spider plate") or wires in order to provide stability. The plate usually is left inside the patient's wrist, while the wires (usually K-wires) have to be removed in a second surgery. This procedure of partial wrist fusion allows for limited wrist movement, whereas total wrist fusion immobilizes the wrist permanently. Following surgery it can take several months for affected patients to regain strength.

Unfortunately both of these operations are salvage procedures and movements in the wrist will be significantly reduced.

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.

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.

The term osteochondrosis has been used to describe a wide range of lesions among different species. There are different types of the prognosis: latens, which is a lesion restricted to epiphyseal cartilage, manifesta, a lesion paired with a delay in endochondral ossification, and dissecans which is a cleft formation in the articular cartilage.

The prognosis for these conditions is very variable, and depends both on the anatomic site and on the time at which it is detected. In some cases of osteochondrosis, such as Sever's disease and Freiberg's infraction, the involved bone may heal in a relatively normal shape and leave the patient asymptomatic. On the contrary, Legg-Calvé-Perthes disease frequently results in a deformed femoral head that leads to arthritis and the need for joint replacement.

Freiberg disease, also known as a Freiberg infraction, is a form of avascular necrosis in the metatarsal bone of the foot. It generally develops in the second metatarsal, but can occur in any metatarsal. Physical stress causes multiple tiny fractures where the middle of the metatarsal meets the growth plate. These fractures impair blood flow to the end of the metatarsal resulting in the death of bone cells (osteonecrosis). It is an uncommon condition, occurring most often in young women, athletes, and those with abnormally long metatarsals. Approximately 80% of those diagnosed are women.

Initial treatment is generally 4–6 weeks of limited activity, often with crutches or orthotics. In rare cases, surgery is necessary to reduce the bone mass of the metatarsal.

The condition was first described by Dr. Alfred H. Freiberg in 1914. He initially thought the condition was caused by acute physical trauma, which is why it was initially called an infraction.

Operations that attempt to restore a blood supply to the lunate may be performed.

Depending on the stage the disease is in when it is discovered, varying treatments are applied.

If X-rays show a mostly intact lunate (not having lost a great deal of size, and not having been compressed into a triangular shape), but an MRI shows a lack of blood flow to the bone, then revascularization is normally attempted. Revascularization techniques, usually involving a bone graft taken elsewhere from the body — often held in place by an external fixator for a period of weeks or months — have been successful at stages as late as 3B, although their use at later stages (like most treatments for Kienböck's) is controversial.

One conservative treatment option would be using an Ultrasound Bone Stimulator, which uses low-intensity pulsed ultrasound to increase vascular endothelial growth factor (VEG-F) and increase blood flow to the bone.

Some Kienböck's patients present with an abnormally large difference in length between the radius and the ulna, termed "ulnar variance", which is hypothesized to cause undue pressure on the lunate, contributing to its avascularity. In cases with such a difference, "radial shortening" is commonly performed. In this procedure, the radius (the lateral long bone) is shortened by a given length, usually between 2 and 5 mm, to relieve the pressure on the dying lunate. A titanium plate is inserted to hold the newly shortened bone together.

During Stage 3, the lunate has begun to break apart due to the pressure of the surrounding bones. This causes sharp fragments of bone to float between the joints, causing excruciating pain. At this point, the lunate is ready for removal. The most frequently performed surgery is the "Proximal Row Carpectomy", where the lunate, scaphoid and triquetrum are extracted. This greatly limits the range of motion of the wrist, but pain relief can be achieved for longer than after the other surgeries.

Another surgical option for this stage is a titanium, silicon or pyrocarbon implant that takes place of the lunate, though doctors shy from this due to a tendency of the implant to smooth the edges of the surrounding bones, thus causing painful pinched nerves when the bones slip out of place.

After the lunate is removed, another procedure, "ulnar shortening" can be performed. This relieves pressure on the newly formed wrist joint of the pisiform, hamate and capitate. Depending on the surgeon, the procedure may be performed the same way as the "radial shortening" where a small section is removed, or the entire top of the ulna may be excised.

At Stage 4, the lunate has completely disintegrated and the other bones in the wrist have radiated downward to fill in the void. The hand now has a deformed, crippled appearance. The only procedure that can be done is the "total wrist fusion", where a plate is inserted on the top of the wrist from the radius to the carpals, effectively freezing all flexion and movement in the wrist. Rotation is still possible as it is controlled by the radius and ulna.

This is currently the last and most complete surgical option for Kienböck's sufferers.

Most of the treatments described here are not mutually exclusive — meaning that a single patient may receive many of them in his quest to relieve pain. For instance, some patients have had casting, bone graft, radial shortening, proximal row carpectomy, and wrist fusion, all on the same hand.

Treatment consists of rest, non-weightbearing and painkillers when needed. A small study showed that the nonsteroidal anti-inflammatory drug ibuprofen could shorten the disease course (from 4.5 to 2 days) and provide pain control with minimal side effects (mainly gastrointestinal disturbances). If fever occurs or the symptoms persist, other diagnoses need to be considered.

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.

The disease can be treated with external in-situ pinning or open reduction and pinning. Consultation with an orthopaedic surgeon is necessary to repair this problem. Pinning the unaffected side prophylactically is not recommended for most patients, but may be appropriate if a second SCFE is very likely.

Once SCFE is suspected, the patient should be non-weight bearing and remain on strict bed rest. In severe cases, after enough rest the patient may require physical therapy to regain strength and movement back to the leg. A SCFE is an orthopaedic emergency, as further slippage may result in occlusion of the blood supply and avascular necrosis (risk of 25 percent). Almost all cases require surgery, which usually involves the placement of one or two pins into the femoral head to prevent further slippage. The recommended screw placement is in the center of the epiphysis and perpendicular to the physis. Chances of a slippage occurring in the other hip are 20 percent within 18 months of diagnosis of the first slippage and consequently the opposite unaffected femur may also require pinning.

The risk of reducing this fracture includes the disruption of the blood supply to the bone. It has been shown in the past that attempts to correct the slippage by moving the head back into its correct position can cause the bone to die. Therefore the head of the femur is usually pinned 'as is'. A small incision is made in the outer side of the upper thigh and metal pins are placed through the femoral neck and into the head of the femur. A dressing covers the wound.

A sequestrum (plural: sequestra) is a piece of dead bone that has become separated during the process of necrosis from normal or sound bone.

It is a complication (sequela) of osteomyelitis. The pathological process is as follows:

- infection in the bone leads to an increase in intramedullary pressure due to inflammatory exudates

- the periosteum becomes stripped from the osteum, leading to vascular thrombosis

- bone necrosis follows due to lack of blood supply

- sequestra are formed

The sequestra are surrounded by sclerotic bone which is relatively avascular (without a blood supply). Within the bone itself, the haversian canals become blocked with scar tissue, and the bone becomes surrounded by thickened periosteum.

Due to the avascular nature of this bone, antibiotics which travel to sites of infection via the bloodstream poorly penetrate these tissues, hence the difficulty in treating chronic osteomyelitis.

At the same time as this, new bone is forming (known as involucrum). Openings in this involucrum allow debris and exudates (including pus) to pass from the sequestrum via sinus tracts to the skin.

Rarely, a sequestrum may turn out to be an osteoid osteoma, a rare tumor of the bone.

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.

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.