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Neurogenic Arthropathy (Charcot Joints)
Neurogenic arthropathy (Charcot joints) is caused by 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.
Any joint can be affected depending on where the nerve damage is located. The most commonly affected joints are 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.
When certain nerves are damaged, people may become unable to sense pain. A variety of disorders, such as diabetes mellitus, spinal cord disorders (such as injuries and syringomyelia), and syphilis, can damage these nerves. The most common causes are diabetes and stroke. People with nerve damage may injure a joint many times 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 joints appear similar to osteoarthritis because the joints are stiff and fluid accumulates in them. Pain is a common early symptom. However, because the ability to sense pain is commonly impaired, the degree of pain is often unexpectedly mild 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 loose pieces of bone and cartilage 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.”
Different joints are affected by different underlying disorders. For example, complications of untreated syphilis affect the knee and hip, and diabetes mellitus affects the foot and ankle. Syringomyelia commonly affects the spine and upper limb joints, especially the elbow and shoulder.
People may develop arthritis that is caused by bacteria (infectious arthritis―see Infectious Arthritis) and may or may not have the fever or general feeling of illness (malaise) that typically occurs with infectious arthritis. This is particularly likely in people with diabetes. Structures such as blood vessels, nerves, and the spinal cord can become compressed due to the tissue overgrowth.
Sometimes Charcot 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. Hip and knee joints may be surgically repaired or replaced. However, artificial joints often loosen and dislocate prematurely.
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