What is Charcot joint? How does it happen? What are the various treatments? Is bone fusion the only option or are there less invasive treatments available?
The Charcot joint, named after a famous French physician, is also called neuropathic joint disease. It consists of severe osteoarthritis (the wear and tear form of arthritis), in a joint that has lost pain sensation due to a neurological condition.
Osteoarthritis itself is the most common form of arthritis seen in this country. It consists of thinning of the cartilage in the joint, with thickening of the underlying bone and proliferation of bone and cartilage at the margins of the joint. It’s most common in the knees and hips, but can occur in any joint. In the legs, osteoarthritis is strongly related to obesity. Injuries to the joints will predispose someone to this arthritis, but there is no evidence that sports, even jogging, will automatically lead to osteoarthritis unless there is also an injury to the joint. Regular osteoarthritis does not progress to a Charcot joint because pain limits the person’s activities, and leads her to protect the joint from painful damage.
A Charcot joint develops when the nerves carrying pain impulses and proprioceptive impulses, (the impulse that tells you what position your joint is in) are damaged.
In the days before antibiotic, Charcot joints were most commonly seen in tabes dorsalis, a form of tertiary syphilis in which the nerves in the spine carrying those joint impulses were destroyed. Now that tertiary syphilis is a rare condition in this country, diabetic neuropathy is the most common condition leading to a Charcot joint.
Other uncommon or rare causes are syringomyelia, in which cystic spaces in the spinal cord lead to loss of sensation; the neuropathy associated with amyloidosis; and leprosy. Even in a disease as common as diabetes and its neuropathy, we seldom see a Charcot joint. I have seen only one or two in my 42 years in general practice.
Because patient with a loss of proprioception don’t feel sensation in the joint it can be overflexed or moved in extreme ways that they ordinarily wouldn’t if they could feel the pain. This damages the joint and its surrounding ligaments.
The result is a joint, or several joints as is common with diabetes, in which the cartilage is broken and fragmented, and the underlying bone has been fractured and disrupted. It’s common to have actual chips of bone break off and float in the joint space. Pain may occur when the underlying bone fractures, but by then the process has already caused a lot of destruction. The persistent trauma causes fluid to build up so that the joint swells and feels mushy. Loose bone fragments can often be felt by an examiner.
Even when the underlying neuropathy can be reversed, it is not possible for the joint to repair itself, as the damage in a Charcot joint is too severe. If it is detected early, splinting and bracing the joint to prevent further damage and reducing weight bearing may slow the progression.
Fusing the joint, which in effect permanently closes it, is often proposed as you note, but the fusion may not take, particularly in a diabetic who can have poor circulation to the foot as well as the neuropathy. Strict immobilization of the joint after the fusion is critical. If surgery to fuse the joint doesn’t succeed, or is refused, the only alternative is a permanent brace.