Dx: “Rocker bottom foot,” Stage III pressure ulcer
The radiograph of the patient’s left foot (FIGURE 1B) revealed extensive collapse of the inner arch and a “rocker bottom foot”—the result of Charcot joint changes. Our patient also had an associated Stage III pressure ulcer.
Charcot joint, also known as neurogenic arthropathy, has been linked to tabes dorsalis, but is more commonly seen in diabetic neuropathy, syringomyelia, spinal cord injury, pernicious anemia, peripheral nerve injury, and from prolonged hydrocortisone injections into the joint.1 The prevalence of Charcot joint in diabetic patients with neuropathy is estimated to be 0.8% to 7.5%. Nine percent to 35% of affected patients have bilateral involvement.2
In patients like ours with diabetic neuropathy, secondary degenerative changes to the joints occur as normal muscle tone, proprioception, temperature perception, and pain perception are lost. The joints become loose, enlarged, and boggy. Though the joint is painless, there can be extensive cartilage erosion or osteophyte formation. The normal plantar and heel forces are increased, producing eccentric loading of the foot, leading to microfractures, ligament laxity, and progression to bony destruction.2
The area of the foot most likely to be involved is the midfoot (70%), with the forefoot and rearfoot comprising the other 30% (15% and 15%, respectively). Charcot joint can occur in a short amount of time in patients with diabetic neuropathy who have experienced even minor trauma.3 In our patient’s case, her trauma history was unknown, though she did comment that her feet initially would ache with walking and then became progressively more disfigured.