Inverse Dynamics Analysis of Knee Joint Kinetics During Squatting: A Cross-Sectional Comparative Study Between Native Healthy Knees and Posterior-Stabilized Total Knee Arthroplasty

A biomechanical evaluation of knee loading during squatting is essential for understanding functional capacity after total knee arthroplasty (TKA). This study compares knee joint kinetics in healthy native knees and in posterior-stabilized TKA (PS-TKA) across BMI categories using 3D motion capture and inverse dynamics. Sixty-two knees (31 healthy, 31 PS-TKA) were analyzed. Native knees demonstrated greater flexion capacity and higher joint loading than PS-TKA knees. Peak resultant joint forces reached 3.50 ± 1.00 BW in healthy knees compared with 2.90 ± 1.20 BW in PS-TKA knees. Healthy knees also generated higher joint moments, with maximum adduction and rotation moments of 5.07% BW × height and 1.29% BW × height, respectively. Body mass index (BMI) significantly influenced loading patterns in native knees, increasing anterior–posterior forces, quadriceps demand, and resultant moments, whereas loading in PS-TKA knees showed minimal BMI dependence. These findings highlight fundamental biomechanical differences between native and prosthetic knees and provide population-specific insights relevant to rehabilitation and high-flexion activities common in Asian populations.