Hip kinematics are associated with gait speed in knee osteoarthritis: A smartphone-based markerless motion capture...

Comprehensive evaluation of gait-related factors in patients with knee osteoarthritis remains limited, particularly the contribution of adjacent joint kinematics. Identifying biomechanical and clinical factors associated with gait performance may improve understanding of walking in knee osteoarthritis. This study examined associations between gait speed, clinical factors, and lower-limb joint kinematics.

Fifty-eight patients scheduled for surgical treatment were enrolled. Preoperative gait speed and lower-limb joint kinematics during walking were assessed using a smartphone-based markerless motion capture system (OpenCap). The hip and knee range of motion during gait was calculated from the kinematic data. Patient characteristics included age, presence of contralateral knee arthroplasty, and knee extensor muscle strength on the affected side. Multivariable linear regression analysis was performed to identify factors independently associated with gait speed.

Greater hip sagittal-plane range of motion (B = 0.0086, 95% CI: 0.003-0.014, p = 0.0009), hip coronal-plane range of motion (B = 0.0090, 95% CI: 0.003-0.015, p = 0.004), and lower-limb muscle strength measured by hand-held dynamometer (B = 0.05, 95% CI: 0.016-0.086, p = 0.005) were independently associated with faster gait speed. Hip kinematic variables collectively explained approximately 35% of the variance in gait speed. The final regression model explained 63% of the variance in gait speed (R² = 0.63; adjusted R² = 0.59).

Hip sagittal- and coronal-plane ROM during walking and knee extensor strength were independently associated with gait speed. These findings highlight the relevance of assessing multi-joint kinematics and muscle strength when characterizing gait performance in individuals with knee osteoarthritis.