Incidence, risk factor analysis, and clinical implications of postoperative constipation in primary knee arthroplasty in a retrospective cohort study

Purpose To investigate primary knee arthroplasty (PKA)-related POC incidence and identify its independent risk factors, focusing on perioperative medications, rehabilitation, and psychological status. Patients and methods A retrospective cohort study was conducted on unilateral PKA patients at our Hospital (January 2022-June 2025). Patients were divided into the Constipation Group (within the first 7 days postoperatively, postoperative 1-week defecation <3 times/week + related symptoms) and the Non-Constipation Group. Clinical data were extracted; univariate and multivariate logistic regression screened risk factors, and ROC curves evaluated predictive value. Results A total of 112 patients were included (Constipation Group: 44 cases, 39.29%; Non-Constipation Group: 68 cases, 60.71%). Multivariate regression identified two independent risk factors: postoperative combination opioid analgesia (OR = 10.74, 95%CI: 4.005-28.803, p < 0.001) and elevated Generalized Anxiety Disorder 7-Item Scale (GAD-7) score (OR = 1.125, 95%CI: 1.02-1.241, p = 0.019). Preoperative Shouhui Tongbian Capsule (SHTB) use and postoperative continuous passive motion (CPM) showed protective trends in univariate analysis ( p < 0.05) but did not reach significance in multivariate models. ROC analysis confirmed acceptable predictive value for the two risk factors (AUC = 0.775 and 0.764). Conclusion POC incidence after PKA is relatively high. Postoperative combination opioid analgesia and elevated GAD-7 score are independent risk factors; preoperative SHTB and postoperative CPM have potential protective effects. These findings support targeted POC prevention in PKA patients.