Charcot foot is a progressive degenerative condition that affects the joints in the feet. It is associated with nerve damage (neuropathy) that decreases the ability to sense stimuli, including pain, and decreases muscular reflexes that control movement. As a result, the joints in the feet are subjected to repeated trauma and injury, causing progressive damage to the ligaments, cartilage, and bones. Charcot foot affects the metatarsal, tarsometatarsal, and tarsal joints, which are located in the forefoot and midfoot.
Incidence and Prevalence
Charcot foot occurs most often in people with diabetes mellitus. It occurs at the same rate in men and women and develops in both feet in approximately 20% of cases.
According to the American Diabetes Association, 60-70% of people with diabetes develop peripheral nerve damage that can lead to Charcot foot and about 0.5% of these patients develop the condition. In most cases, onset occurs after the age of 50, and after the patient has had diabetes for 15 to 20 years.
Risk Factors and Causes
Diabetes mellitus and peripheral neuropathy are the primary risk factors for Charcot foot. High levels of glucose in the blood (chronic hyperglycemia), which is the hallmark of diabetes, can trigger neuropathy, which then may proceed to Charcot foot. Precisely how this process occurs is unknown.
Signs and Symptoms
While peripheral neuropathy develops over decades, the progression of Charcot foot can occur in a matter of weeks or months. Minor trauma, such as twisting the foot, can initiate the process and the loss of pain perception and the sense of foot position can result in repeated joint injuries.
Symptoms of Charcot foot include the following:
Dislocation of the joint
- Insensitivity in the foot
- Instability of the joint
- Strong pulse
Swelling of the foot and ankle (caused by synovial fluid that leaks out of the joint capsule)
Subluxation (misalignment of the bones that form a joint)
Nerve damage causes muscle weakness and slack ligaments, which result in joint instability and subsequent subluxation and/or dislocation. Subluxation initiates the process of degenerative joint disease (arthropathy). The ends of misaligned bones grind against each other and fragments of bone and cartilage enter joint and often produce a coarse grating sound (audible crepitus) when the joint is moved. The physician may be able to feel these fragments in the joint.
Deformity of the foot, which occurs in advanced disease, is caused by joint displacement and/or dislocation, bone overgrowths (osteophytes), and fractures. Osteophytes may protrude from the top of the foot as the body forms new bone to replaces bone loss. Fractures may cause the tarsal bones to collapse, resulting in an outward bowing of the arch (called “rocker foot”).
Complications of Charcot foot include calluses and ulcers, which occur when bony protrusions rub inside the shoes and may become infected. Bone inflammation (osteomyelitis) and inflammation of the joint membranes (septic arthritis) also may develop. Septic arthritis may manifest with malaise and fever.
Blood vessel and nerve compression may occur and often do not cause symptoms due to the loss of sensation in the foot.
Diagnosis is based on medical history (i.e., history of diabetes), symptoms, imaging tests (e.g., x-rays, MRI), and laboratory tests.
X-rays are used to detect joint effusions, large osteophytes, fractures, bone fragments, and joint misalignment and/or dislocation. Magnetic resonance imaging (MRI) can be used to help differentiate between Charcot foot and osteomyelitis (bone infection). Joint margins, which are clearly defined upon MRI in Charcot foot, appear blurred in osteomyelitis.
Laboratory tests include drawing fluid from the joint (arthrocentesis) to detect bone and cartilage fragments and blood, which may be present in some cases of Charcot foot.
The goal of treatment is to stabilize the joint. In patients with diabetes, restraining from placing weight on the foot for at least 8 weeks may help to prevent further damage. During this time, a total contact or walking cast and crutches may be required to protect the foot.
Surgery may be necessary to treat severe deformities or recurring ulcers by reshaping structures within the foot or removing bony protrusions that cause ulcers. After surgery, the foot is monitored for signs of infection (e.g., redness, swelling, warmth).
In most cases, patients with Charcot foot can resume regular activities after treatment. In patients with diabetes, blood sugar levels, injuries to the foot, and recurrence of the disease must be strictly monitored.
For more information see one of the Doctors of the New Mexico Foot & Ankle Institute. Please call 505-880-1000 to schedule an appointment.