Paratibial cyst associated with wear debris after total knee arthroplasty

We present a case in which a synovial cyst arose from the proximal tibia and expanded in the calf of a patient after total knee arthroplasty. A cystogram showed a direct communication between the joint cavity and the cyst, apparently associated with a screw that penetrated the tibial cortex. Histologic examination of the cyst showed an inflammatory reaction, including macrophages, foreign body giant cells, and metal and polyethylene particles. To our knowledge, this is the first case report illustrating a paraosseous cyst that developed after total knee arthroplasty. Wear debris from the total knee prosthesis may have been responsible for this unusual cyst.