Charcot arthropathy, often called Charcot foot, is a progressive joint disorder that primarily affects the foot and ankle. It is linked to peripheral neuropathy, typically caused by diabetes, which results in a loss of sensation. This lack of protective sensation prevents the feeling of pain or trauma, leading to repeated, unrecognized micro-injuries to the bones and joints. Charcot arthropathy results in a destructive cycle of bone fragmentation, joint dislocation, and eventual severe deformity.
The disease progression is classified using the modified Eichenholtz classification, based on clinical signs and radiographic findings. This system guides diagnosis and treatment, as the acute phase can advance rapidly. The four stages—Stage 0, Stage 1, Stage 2, and Stage 3—describe the evolution from initial inflammation to the final, stable deformity.
Acute Inflammation and Initial Presentation (Stage 0)
This is the earliest phase of Charcot arthropathy, often called the prodromal or pre-Charcot stage. It was added to the original Eichenholtz classification to describe the initial inflammatory presentation. The foot shows distinct signs of inflammation, including localized swelling, redness, and increased skin temperature (calor). The affected foot may feel three to seven degrees Celsius warmer than the unaffected side.
Pain may be minimal or absent due to the underlying neuropathy, which often delays detection. Since symptoms can mimic other conditions, such as deep vein thrombosis or cellulitis, a high degree of suspicion is required for diagnosis. Standard X-rays often appear normal at this point, showing no significant bone or joint changes.
Advanced imaging like Magnetic Resonance Imaging (MRI) is often used to confirm the diagnosis and rule out other issues. An MRI can reveal bone marrow edema, a sign of inflammation and micro-trauma within the bone structure, before the bone architecture collapses. Early diagnosis and immobilization at Stage 0 can prevent progression to a destructive stage and minimize long-term deformity.
Fragmentation and Joint Destruction (Stage 1)
Stage 1 marks the onset of the destructive phase, originally termed the developmental stage by Eichenholtz. The weakened bones begin to break apart under normal stress, leading to significant bone fragmentation, joint subluxation, and dislocation. This destructive process is driven by continued, unperceived weight-bearing on the unstable foot.
Radiographic evidence becomes clear, showing characteristic signs like bone debris at the joint margins and clear fractures. The soft tissues remain swollen, and the foot is still warm and red, indicating the acute inflammatory process is active. The mechanical collapse of the foot’s arch begins during this phase, which can rapidly lead to a physical deformity.
This phase represents the peak of active joint destruction, severely compromising the structural integrity of the foot. Treatment focuses on immediate, aggressive non-weight-bearing immobilization, typically with a total contact cast, to stop bone damage progression. If the destructive cycle is not halted, the foot’s anatomy will continue to collapse, leading to a difficult long-term outcome.
Coalescence and Repair (Stage 2)
Stage 2, the coalescence stage, represents the intermediate phase where the body shifts from active destruction toward repair. Clinically, acute signs of inflammation begin to subside, with a decrease in redness, warmth, and swelling compared to earlier stages. The active breakdown of bone slows significantly.
Radiographically, healing becomes evident as the body attempts to consolidate fragmented bone pieces. Fine bone debris starts to be absorbed, and larger fracture fragments begin to fuse. This fusion results in a hardening of the bone ends, known as sclerosis, which is visible on X-rays.
Despite the slowing of destruction and the beginning of repair, the joint remains unstable and the foot architecture is compromised. Management maintains off-loading and immobilization, allowing bone fragments to knit together in the least deformed position possible. This stage marks the transition toward a more stable but still deformed foot structure.
Consolidation and Residual Deformity (Stage 3)
The final stage, Stage 3, is the consolidation or reconstruction phase, signifying the resolution of the acute process. All signs of inflammation, including warmth and swelling, have resolved, and the foot is considered structurally stable. Radiographs confirm that the fusion and remodeling of bone fragments are complete.
The main characteristic is a permanent structural deformity resulting from the earlier joint collapse. This often manifests as the “rocker-bottom” foot, where the arch collapses inward, causing the middle of the foot to bulge downward. Although the bone structure is rigid and fused, the deformity creates abnormal pressure points on the sole of the foot.
This residual deformity requires lifelong management to prevent serious complications, even though the active disease is resolved. Specialized footwear and orthotics are necessary to redistribute pressure and protect the skin from breakdown. This protection is vital, as breakdown can lead to chronic ulceration and infection.