A Giant Thigh Mass in a Patient With Total Knee Arthroplasty for Charcot Joint

&NA; A painless and progressively growing mass consisting of fibronecrotic quadriceps femoris muscles with a giant multilobular cystic cavity formed 15 years after total knee arthroplasty for Charcot joint. It was considered to be a cyst from the knee joint accompanied by compartmental muscular necrosis. The painless and progressively growing nature of the mass seemed to be largely attributable to a neuropathic joint. Computed tomography proved to be helpful for diagnosis. Conservative management was unsuccessful in relieving the symptoms.