The popliteal cysts after total knee arthroplasty ( TKA ) are rarely seen clinically. While a painful and enlarging mass at the popliteal fossa can be frequently found, and associated with lower leg swelling and limited range of motion of the knee joint. The diagnosis can be made based on the local type-B ultrasonic inspection. The cyst excision is the main therapeutic method, and meanwhile revision TKA should be considered. The pathological examination after the operation showed there are a lot of wear particles of joint prostheses in the cyst wall and lfuid. In general, the cyst recurrence will not occur after the excision. Even through this kind of lesions are infrequent, it may be suggested that the wear or loosening of joint prostheses exists. So routine follow-up is critical in patients with TKA for early detection of possible problems of joint prostheses.