Abstract: BACKGROUND: Total knee arthroplasty is one of the effective methods to treat end-stage knee osteoarthritis. However, some patients still experience chronic post-surgical pain. It is significant to find out the influencing factors of chronic post-surgical pain. Demographic factors, social psychological factors and perioperative pain were the focus of previous studies, but muscle factors closely related to the occurrence and development of knee osteoarthritis were rarely reported. 
OBJECTIVE: To evaluate the value of preoperative quantitative ultrasound analysis of quadriceps femoris in predicting chronic post-surgical pain after total knee arthroplasty. 
METHODS: A total of 250 patients with knee osteoarthritis who underwent the first unilateral total knee arthroplasty under elective general anesthesia from January to August 2022 in the Affiliated Hospital of Xuzhou Medical University were selected. All patients were treated with the same anesthesia and operative methods. Before the surgery, clinical data were recorded, and the thickness and echo intensity of quadriceps femoris on the operated side were measured by ultrasound imaging, which could quantify the degree of quadriceps femoris atrophy. Multivariate logistic regression was used to analyze the independent factors affecting the occurrence of chronic post-surgical pain, and receiver operating characteristic curves were used to evaluate its predictive value. 
RESULTS AND CONCLUSION: (1) 250 subjects were involved in the result analysis, and 91 of them had chronic post-surgical pain, with an incidence of 36.4%. (2) There were significant differences between the chronic pain and non-chronic pain groups in preoperative pain score during movement, preoperative Western Ontario and McMaster University Osteoarthritis Index, preoperative anxiety and depression scale score, preoperative muscle thickness and echo intensity of quadriceps femoris, and postoperative acute pain score (P < 0.05). (3) Multivariate logistic regression analysis showed that preoperative thickness of quadriceps femoris was an independent protective factor for chronic post-surgical pain and preoperative pain score during movement was an independent risk factor for chronic post-surgical pain. (4) Receiver operating characteristic curves showed that the area under the curve of the preoperative thickness of quadriceps femoris was 0.625 (95%CI: 0.555-0.695), and the critical value was 2.78 cm, sensitivity was 0.802, specificity was 0.415. (5) It is concluded that the preoperative thickness of quadriceps femoris is an independent protective factor for chronic post-surgical pain, but its predictive efficacy is low, and its clinical application needs to be further verified or modified. 

Key words: quadriceps femoris, ultrasound, quantitative analysis technique, total knee arthroplasty, chronic post-surgical pain