Patellar clunk syndrome after posterior stabilized total knee arthroplasty.

Two hundred thirty-six posterior stabilized total knee arthroplasties (TKAs) were performed consecutively. Twenty-seven patellar clunk syndromes were identified in 25 patients. Insall-Salvati ratio, position of joint line, postoperative patellar height, and anterior-posterior position of tibial tray were measured. It was found that postoperative low-lying patella (P<.001) and anterior placement of tibial tray (P=.011) was associated with patellar clunk syndrome. Thirteen patients had bilateral TKAs of the same prosthesis (5 bilateral AMK knees and 8 bilateral Insall Burstein knees) but unilateral patellar clunk syndrome. The nonclunk sides were used as control for comparison with the clunk sides. The congruency and tilting of the patellar button in the skyline view were documented. It was observed that the congruency of the patellar button was less satisfactory in the clunk side (P=.019).