Avascular necrosis is a rare condition in which an area of bone in the knee joint loses it's blood supply and may die. The dead bone becomes weak and may collapse causing a fracture and collapse of the joint surface which may in turn lead to arthritis. Although there are recognised causes such as alcoholism and deep sea diving, most patients with avascular necrosis have no apparent cause.
The main symptom with avascular necrosis is pain. It can be difficult to diagnose without special tests as x-ray changes only occur towards the terminal stages of this pathology. It is best diagnosed with a bone scan or an MRI scan.
Treatment is also difficult. If the condition is caught early enough decompression of the affected area may be successful but in most cases the treatment is addressed to treating the complications of the condition and may require a partial joint replacement in some cases.