Charcot arthropathy: neuropathy and unnoticed injury

Charcot arthropathy is the progressive destruction of the bones, joints and soft tissues (such as ligaments and tendons) of the foot, and sometimes the ankle, in a person with neuropathy. Neuropathy means damage to the peripheral nerves, the nerves outside the brain and spinal cord. Diabetes is the commonest cause of the neuropathy, but other nerve disorders can produce the same picture. The condition is uncommon in the general population.

The mechanism is a chain. Nerve damage removes protective sensation, the pain that normally makes us rest an injured foot. Small fractures and sprains therefore go unnoticed, and walking carries on. This repeated microtrauma (tiny injuries that add up) sets off inflammation that makes osteoclasts, the cells that break bone down, overactive compared with osteoblasts, the cells that build bone. Bone is lost faster than it is rebuilt, and the result is fracture, joint displacement, instability and deformity.

The foot can become warm and swollen with little pain, so a damaged foot in a person with neuropathy may be relatively comfortable. If the midfoot collapses, a rocker-bottom foot can develop, in which the sole bulges downward like the base of a rocking chair.

Reduced pain is a sign of lost protection, not reassurance that the foot is healthy. In a person with neuropathy, a warm, swollen foot should be treated as Charcot until proven otherwise, and the foot is protected from weight bearing (offloading) to limit further collapse. Infection can look similar and can coexist, so it still has to be considered. Treatment usually involves prolonged offloading, often for several months.