Incidence and Associated Factors of Patellar Clunk Syndrome After Total Knee Arthroplasty: A Retrospective Single-Center Study

Objective: Patellar clunk syndrome (PCS) is an uncommon complication after total knee arthroplasty (TKA), particularly in posterior-stabilized prostheses. It is characterized by a painful catching or “clunk” during knee extension, often caused by fibrous nodule formation at the superior pole of the patella. Reported incidence rates vary widely, and although factors such as implant design, femoral component size, and insert thickness have been proposed, the true incidence and risk factors remain uncertain.Method: This retrospective study included 330 patients who underwent primary TKA between 2016 and 2018. Demographics, implant design, femoral component size, insert thickness, and radiographic parameters were analyzed. Clinical outcomes were assessed using the Knee Society Score (KSS), and ultrasonographic detection of suprapatellar fibrous nodules was performed.Results: PCS occurred in 23 patients (7.5%). Incidence was higher in men (12.5% vs. 5.8%, p=0.041), in posterior-stabilized compared with cruciate-retaining prostheses (8.5% vs. 3.1%, p=0.048), and in bilateral versus unilateral procedures (30.4% vs. 5.2%, p