Joint loading asymmetries in knee replacement patients observed both pre- and six months post-operation

Background Studies have highlighted asymmetries in knee joint moments in individuals with osteoarthritis and joint replacements. However, there is a need to investigate the forces at the knee joints to establish the extent of loading asymmetries. Methods Twenty healthy (mean age, 62; range, 55-79 years) and 34 pre- to post-knee arthroplasty (mean age, 64; range, 39-79 years) participants performed gait and sit-stand activities in a motion capture laboratory. Knee joint forces and moments were predicted using inverse dynamics and used to calculate peak loading and impulse data which were normalized to body weight. Comparisons were made between affected and contralateral limbs, and changes from pre- to post-knee arthroplasty. Findings Pre-knee arthroplasty peak vertical knee forces were greater in the contralateral limb compared to the affected limb during both gait 3.5 vs. 3.2 â̂ - body weight and sit-stand 1.8 vs. 1.5 â̂ - body weight. During gait, peak knee adduction moment asymmetries significantly changed from pre- to post-knee arthroplasty (- 0.3 to 0.8 â̂ - % body weight â̂ - m â̂ - height), although differences in vertical knee forces remained. There were no significant changes in loading during sit-stand from pre- to post-knee arthroplasty. The healthy participants showed no noteworthy asymmetries. Interpretation This study showed loading asymmetries in knee forces between affected and contralateral limbs both pre- and post-knee arthroplasty. Continued over reliance of the contralateral limb could lead to pathology.