Multilobulated popliteal cyst after a failed total knee arthroplasty

Popliteal cyst is a rare finding after total knee arthroplasty (TKA), but when present, it might indicate a malfunction of the TKA related to generation of wear‐particles, or loosening. We present a case of a multilobulated popliteal cyst developing in a patient 8 years after primary TKA. The cyst was associated with a mechanical prosthetic loosening. The primary complaint of the patient was pain in the posterior region of the knee. A two‐stage procedure consisting of cyst excision at first, followed after 5 months by a revision TKA was performed. Intraoperatively, a darkish, multilobulated cyst with a well‐defined thick wall filled with fluid containing polyethylene debris, communicating with the knee joint was found. After 3 years of follow‐up, the patient was satisfied and walked without the support of a cane. The patient presented a satisfactory knee range of motion. Clinical, radiological and ultrasound investigations ruled out popliteal cyst recurrence. A dissecting popliteal cyst associated with a failed TKA should be excised because it contains polyethylene debris that constitutes an induced factor for prosthetic loosening. A two‐stage procedure with quite a long time in‐between, as presented in this paper, can be a useful alternative to manage such a problem, in particular in very old patients associated with other medical problems.