Reference Intervals of Muscle Strength and Motion Range of the Knee Joint on the Side Opposite to Knee Arthroplasty

Abstract

[Purpose] The assessment of non-operative knee function is important for the recovery of activities of daily living (ADL) of patients with knee arthroplasty. Therefore, we established reference intervals (RIs) for knee muscle strength and range of motion, taking into account the factors that affect values before and after surgery. [Participants and Methods] We evaluated knee muscle strength and range of motion in knee extension and flexion, as well as knee extension and flexion joint range of motion in 390 patients who had undergone knee arthroplasty, excluding those who had undergone the same surgery on the opposite side. The partitioning of RI by these factors was judged using the standard deviation ratio (SDR) representing the magnitude of between-subgroup differences. Variables were evaluated, and the SDR was calculated, and 0.3 was used as a stratification criterion. [Results] From the SDR values, it was judged that each muscle strength and each range of motion should be stratified by gender and by whether the knee arthropathy was unilateral or bilateral. The RIs were established using the Box-Cox parametric method for muscle strength and by a nonparametric method for range of motion. [Conclusion] The reference range of non-operative knee function is useful for evaluating knee function before and after surgery.