In 2005, the CDC estimated that 20.8 million people in the United States, or 7% of the population, were living with diabetes.1 Peripheral neuropathy, a major complication of diabetes found in nearly 30% of diabetic patients aged 40 years or older,1 plays an integral role in the development of Charcot's arthropathy.
Dr. Jean-Martin Charcot first described a process of bone and joint destruction associated with syphilis-induced neuropathy in 1868 with detailed accounts of tabes dorsalis. 2 Although Charcot's arthropathy was first described as a sequella of tertiary syphilis, diabetes is now the most common cause of neuropathic arthropathy in the Western world. Charcot's arthropathy is a chronic, progressive disease of bone and joints, most commonly found in the feet and ankles of patients with diabetes and peripheral neuropathy.
All health care providers treating patients with diabetes should be aware of the potential for Charcot's arthropathy to develop. Early recognition and proper treatment can prevent progressive deformity, ulcer formation, infection, and even limb amputation.
PATHOPHYSIOLOGY
Although the exact etiology of Charcot's arthropathy is unknown, two major theories have been proposed. The neurotraumatic theory suggests that peripheral neuropathy leads to a lack of proprioception, which in turn causes ligament laxity. This results in increased joint range of motion, instability, and repetitive minor trauma. The inflammatory response to this microtrauma then causes increased bone resorption and weakening, leading to increased susceptibility to fractures and joint damage.
The neurovascular theory suggests that damage to trophic centers of the nervous system results in altered sympathetic control. This leads to increased blood flow to bones and greater bone resorption, resulting in osteopenia. The osteopenic bones are thus weakened and more susceptible to fracture and joint damage.
Despite the differences in these two theories, four factors are necessary for neuropathic arthropathy to develop: peripheral neuropathy, an unrecognized injury, continued repetitive stress on injured structures, and increased local blood flow.3
CLINICAL PRESENTATION
Charcot's arthropathy typically manifests in patients with long-standing diabetes and peripheral neuropathy. Patients are commonly in their fifth or sixth decade of life. The initial signs of Charcot's arthropathy are often subtle and can easily be overlooked. Unilateral foot swelling or difficulty with proper shoe fitting in a patient with diabetes should alert the health care provider to the possibility of Charcot's arthropathy.
Acute Charcot's arthropathy typically manifests as a painless, warm, erythematous, edematous foot with or without a history of trauma. In addition, the patient will usually have a bounding pedal pulse and neuropathy on examination. These findings, however, often lead to a misdiagnosis of cellulitis or osteomyelitis.
ANATOMIC CLASSIFICATION
Multiple classification systems were developed to describe Charcot's arthropathy based on the location of the 
joint destruction (see Figure 1). Brodsky's system, which is based on the four most common regions affected, is perhaps the most widely used.4
Type 1 indicates the tarsometatarsal (Lisfranc's) region. Approximately 60% of cases of Charcot's foot occur in this region.5 Residual deformity in this area manifests as a collapse of the longitudinal arch, resulting in a rocker-bottom foot (see Figure).
Type 2 indicates the hindfoot. This region is the second most common site for Charcot's arthropathy to develop.
Type 3a indicates the ankle joint. Type 3b indicates the posterior calcaneous.
Type 4 indicates that multiple regions are involved. Each region may be at a different stage of the Eichenholtz classification system.
Type 5 indicates the forefoot. This region is an uncommon site of Charcot's arthropathy.