Objective To develop a sedentary behavior intervention program for elderly patients after hip and knee arthroplasty based on the Integrated Theory of Health Behavior Change (ITHBC) and to evaluate its effectiveness in clinical practice.Methods A convenience sampling method was used to randomly assign patients who revisited the orthopedic outpatient department from September to November 2024 into a control group (n=34) and an intervention group (n=35).The intervention group received nursing care guided by the sedentary behavior intervention program developed under the ITHBC framework.The program was constructed through a literature review and two rounds of Delphi expert consultation.The control group received routine nursing care.Outcomes were evaluated immediately after the intervention and two months later.Results At both immediate post-intervention and two-month follow-up assessments, there were statistically significant differences between the two groups in total sedentary time, total physical activity, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score, and exercise self-efficacy (all P＜0.05).Significant group effects, time effects, and interaction effects were observed for these variables (all P＜0.05).Conclusion Implementation of the sedentary behavior intervention program based on the ITHBC effectively reduces sedentary behavior, increases overall physical activity, promotes joint functional recovery, and enhances exercise self-efficacy among elderly patients after hip and knee arthroplasty.