Smartphone-Based Assessment of Postural Balance in Patients With End-Stage Knee Osteoarthritis: A Cross-Sectional Study.

Background Osteoarthritis is the most prevalent joint disease and significantly impacts quality of life, particularly by increasing the risk of falls due to balance impairments. Individuals with knee osteoarthritis often experience musculoskeletal deficits that compromise proprioception and postural stability. While traditional tools for assessing balance, such as force platforms and motion capture systems, are effective, they are also costly and less accessible in clinical settings. Advances in mobile technology have enabled the use of smartphone-based inertial sensors as a practical alternative for evaluating postural control. However, evidence supporting their application in patients with end-stage knee osteoarthritis remains limited, especially regarding their association with physical function. Materials and methods This cross-sectional study included 40 participants, divided into knee osteoarthritis (n = 20) and control (n = 20) groups. Participants completed four static balance tasks while acceleration data were recorded using a smartphone. The tasks consisted of semi-tandem and parallel feet stances, performed with eyes open and closed. Each task was repeated twice for 30 seconds, with a one-minute rest between trials. In the knee osteoarthritis group, physical function was further assessed using the Timed Up and Go (TUG) test and the 30-second chair stand test. Acceleration data were processed to compute the root mean square values for body sway in the antero-posterior and medio-lateral directions, as well as overall acceleration magnitude. Results The Mann-Whitney U-test revealed significant differences between groups in most tasks and parameters, with the knee osteoarthritis group exhibiting significantly higher body acceleration. Furthermore, increased body sway was significantly correlated with poorer physical function, particularly in semi-tandem tasks. Conclusion Our findings suggest that smartphone-derived measurements provide an effective means of assessing postural control in patients with end-stage knee osteoarthritis, offering valuable insights for managing fall risk and informing tailored rehabilitation strategies.