Charcot's joints (neurogenic arthropathy, neuropathic arthropathy) is progressive joint destruction, often very rapid, that develops because people cannot sense pain and thus are not aware of the early signs of joint damage.
When certain nerves are damaged, people may become unable to sense pain. A variety of disorders, such as diabetes mellitus, spinal cord disorders, and syphilis, can damage these nerves. People with nerve damage may injure a joint many times, or even fracture it, without noticing. Injuries may occur for years before the joint malfunctions. However, once it malfunctions, the joint may be permanently destroyed within a few months.
In its early stages, Charcot's joints appear similar to osteoarthritis, because the joint is stiff and fluid accumulates in it. Usually, the joint is not painful or is less painful than would be expected considering the amount of joint damage. If the disorder progresses rapidly, the joint can become extremely painful. In these cases, the joint is usually swollen because of excess fluid and abnormal bone growth. It may look deformed because it has been fractured and ligaments have stretched, allowing the bones to slip out of place. Moving the joint may cause a coarse, grating sound because of bone fragments floating in the joint. The joint may feel like a “bag of bones.”
Any joint can be affected depending on where the nerve damage is—most commonly, the knee or ankle or, in people who have diabetes, the foot. Often, only one joint is affected, and usually not more than two or three.
Doctors suspect Charcot's joints when people have a nerve disorder and joint problems. X-rays can detect joint damage, which often includes calcium deposits and abnormal bone growth. Sometimes Charcot's joints can be prevented by taking care of the feet and by avoiding injuries. Splints or special boots can sometimes help protect vulnerable joints. Treatment of the underlying nerve disorder can sometimes slow or even reverse joint damage. Diagnosing and immobilizing painless fractures and splinting unstable joints can help stop or minimize the damage. Hips and knees may be surgically repaired or replaced. However, artificial joints often loosen prematurely.
Resource: Merck Manual Home Edition