Enlarging, Multilobulated Popliteal Cyst After Total Knee Arthroplasty

CASE: A 69-year-old woman presented with a 5-year history of an enlarging popliteal cyst 7 years after total knee arthroplasty (TKA). Magnetic resonance imaging revealed a large, multilobulated popliteal cyst. Initial diagnostic workup was inconclusive but repeat evaluation met criteria for culture-negative prosthetic joint infection (PJI). She underwent revision TKA, intraoperative cultures identified Micrococcus luteus, and she remains on antibiotic suppression. At her 4-year follow-up, she demonstrated complete resolution of the popliteal cyst with minimal pain. CONCLUSION: Popliteal cysts may represent a primary presenting symptom of PJI, especially when the causative organism is of low virulence, such as M. luteus.