Objective To explore the behavioral characteristics and population differences in home-based rehabilitation exercise among older patients after unicompartmental knee arthroplasty(UKA), and to provide a reference for developing precise and individualized rehabilitation interventions. Methods A descriptive qualitative study was conducted using purposive sampling to recruit 22 older patients who had undergone UKA. Guided by the Capability, Opportunity, Motivation-Behavior (COM-B) model, data related to rehabilitation exercise were collected through semi-structured interviews. Content analysis was employed to identify thematic dimensions and labels associated with rehabilitation exercise behaviors. User clustering was subsequently performed to classify patient groups, and WordArt software was used to visualize user profiles. Results Four thematic dimensions and 17 core labels were identified. Based on cluster analysis, four typical user profiles were generated:proactive and self-disciplined users, guidance-dependent users, insufficiently motivated users, and anxiety-prone users. Conclusion Home-based rehabilitation exercise behaviors among older patients who had undergone UKA were influenced by the multidimensional interaction of capability, opportunity, and motivation factors, resulting in significant intergroup differences. Based on the COM-B model and user profile characteristics, targeted intervention strategies can be developed from three core aspects:enhancing rehabilitation capability, creating rehabilitation opportunities, and strengthening rehabilitation motivation. Such strategies may optimize the rehabilitation support system and improve patients′ adherence to and effectiveness of rehabilitation exercise.