This is a condition that affects the feet and ankles of patients with decreased sensation in their feet. Because of this lack of sensation, these patients are unable to feel pain and thus overload their feet without being consciously aware of it. This can then lead to gradual weakening of the bones resulting in multiple small fractures in the bones and joints of the foot and ankle with minimal feedback that this is occurring. Over time the foot or ankle that is affected becomes unstable and deforms gradually, often resulting in a rocker-bottom foot deformity that typifies the Charcot foot.
At present the most common cause in high income countries for decreased sensation in the feet is nerve damage due to longstanding diabetes. Other conditions that may affect the sensory nervous system leading to Charcot foot deformities include, but are not limited to:
- Alcohol abuse
- Cerebral palsy
- Insensitivity to pain from birth
- Charcot-Marie-Tooth disease
- Spinal nerve damage or extremity nerve damage
- Spina bifida
Patients who develop these deformities end up with abnormal bony prominences under the skin which leads to areas of high pressure. As they do not feel pain from these areas, they overload these areas and the overlying skin breaks down due to overload and decreased local blood supply. This results in pressure sores which are prone to infection, often leading to deep infections all the way into the bone. When infection involves the bone, there is a very significant risk that these patients will end up with a major amputation of the involved extremity. The aim of early treatment is to avoid the development of the bony prominences, subsequent wounds, infections and amputations.
Typically, the acute Charcot foot will present as a red, warm and swollen foot in someone who has had longstanding diabetes. There will often be no recall of a preceding injury. If there is, it is usually a very minor injury. The person may report a crunchy sensation in the bones of the foot and a gradual change in the shape of the foot. This is due to the ongoing small breaks and deformities in the bones of the foot. Due to decreased sensation, there is remarkably little pain as this occurs, but discomfort may be present.