Functional mobility profiles in pre-operative knee osteoarthritis patients: A cluster analysis of self-report, in-clinic, and free-living measures.

Abstract

Mobility assessment in knee osteoarthritis spans perception (patient-reported outcomes), capacity (in-clinic performance), and performance (free-living behaviour). By integrating all three domains, this study explored emerging pre-operative mobility phenotypes. Fifty-six patients awaiting knee arthroplasty completed patient-reported measures (Oxford Knee Score (OKS), quality of life (EQ-5D)), in-clinic testing with markerless motion capture (60-s preferred-pace and, in a subset, 30-s fast-paced walk and five-repetition sit-to-stand), and seven days of free-living monitoring with shank-mounted inertial sensors (steps, sedentary time, stride time). Hierarchical clustering was applied to standardized features in two models: Model 1 (n = 56; in-clinic preferred-pace walk) and Model 2 (n = 37; included in-clinic fast-pace walk and sit-to-stand time). Principal component scores (PCs) described knee kinematics. An exploratory tertile transition analysis tracked cross-domain consistency. Both models yielded two phenotypes: a smaller low-functioning group and a larger higher-functioning group. The low-functioning group had higher body mass index and more females, worse self-reported function and quality of life (OKS, EQ-5D), slower in-clinic gait, and lower free-living activity (fewer daily steps, greater sedentary time) with slower gait (longer stride time). The PCs revealed reduced knee flexion magnitude and range of motion, as well as a varus-thrust-like pattern in the low-functioning group. Within the higher-functioning group, only 11-15% of patients remained in the same tertile across domains. The unified mobility assessment identified two distinct pre-operative mobility phenotypes with substantial cross-domain heterogeneity among higher-functioning patients. The implications of this assessment approach may support domain-specific interventions to personalize care and potentially improve recovery after knee arthroplasty.