Introduction
Osteonecrosis is the dying off of the bone. This is theoretically possible all over the body, but the knee is one of the most frequently affected joints. Women are slightly more frequently affected than men (ratio about 3:1).
Causes
A subdivision of osteonecrosis is performed in septic and aseptic manner. An infection of the bone at the knee can occur after knee joint surgery, for example. In the case of aseptic bone necrosis, the death of the bone is not due to an infection with bacteria.
The specific causes are not yet fully understood. Circulatory disorders are considered a possible cause of aseptic bone necrosis. For example, in the case of repeated overloading or trauma caused by minor vascular injuries, the bone can no longer be adequately supplied with oxygen from the blood.
As a result, the tissue that is insufficiently supplied with oxygen dies. Another possibility for blood deprivation is an embolism of the supplying arteries. This can occur, for example, in the context of caisson disease, which is known as diver’s disease.
If a diver emerges too quickly, the artificially supplied breathing gases can clog arteries and thus lead to various late effects. One of them is that the bone dies off in the course of the weeks. Risk factors that can promote the development of osteonecrosis are radiotherapy of the affected knee in the past or long-term cortisone therapy. Alcohol consumption and smoking are also discussed as stimuli.
Symptoms
A typical symptom of osteonecrosis of the knee is load-dependent pain in movement. In severe cases, the knee may also hurt at rest. An additional symptom is an effusion of the knee joint, which usually occurs only when there is a major defect and is manifested by swelling. Depending on the cause, for example an infection, signs of inflammation such as fever or overheating of the affected area may also be present.
Osteochondrosis dissecans
Osteochondrosis dissecans is an aseptic bone necrosis below the articular cartilage that preferentially affects the knee and, if unchecked, ends in the rejection of bone-cartilage fragments (dissectate, articular mouse) from the articular surface. If the articular mouse is trapped, it may be responsible for a joint lock.
