Objective:To analyze the risk factors for patellar clunk syndrome after total knee arthroplasty (TKA) without patellar surface replacement.Methods:Retrospectively analyzed were a total of 222 patients who had undergone TKA without patellar surface replacement at Department of Joint Surgery, The Second Hospital of Shanxi Medical University from June 2020 to June 2021. There were 43 males and 179 females, and 38 cases of rheumatoid arthritis and 184 cases of arthritis. They were divided into a patellar clunk syndrome group ( n = 56) and a non-patellar clunk syndrome group ( n = 166) according to the occurrence of patellar clunk after TKA. The incidence of early patellar clunk syndrome after TKA was 25.2% (56/222). The patient gender, arthritis type, prosthesis type, postoperative range of knee motion, postoperative patellar thickness, Insall-Salvati index, postoperative joint line height, lower extremity muscle strength, and the distance from the tibial plateau to the patellar tendon were recorded. The risk factors for patellar clunk syndrome were determined by univariate analysis and logistic analysis. Results:The univariate analysis showed significant differences between the 2 groups in prosthesis type, postoperative joint line height, postoperative lower extremity muscle strength, and the distance from the tibial plateau to the patellar tendon ( P < 0.05). The logistic analysis showed that the posterior cruciate substituting (PS) prosthesis was an independent risk factor compared with the cruciate-retaining (CR) prosthesis ( OR = 2.791, 95% CI: 1.411 to 5.521, P = 0.003), and the increased lower extremity muscle strength was an independent protective factor ( OR = 0.295, 95% CI: 0.148 to 0.587, P = 0.001). Conclusions:The incidence of patellar clunk syndrome is relatively high. The PS prosthesis may be an independent risk factor relative to the CR prosthesis. As the increased lower extremity muscle strength may be an independent protective factor, the recovery and strengthening of the muscle strength after TKA require more attention.