Are the Current Outcome Measurement Tools Appropriate for the Evaluation of the Knee Status in Deep Flexion Range?

We determined whether current outcome measurement tools are appropriate for the evaluation of the knee status in deep flexion range after TKA. Patients (n = 604) with more than 120° of knee flexion were evaluated by Knee Society score, WOMAC, and high flexion knee score (HFKS). The appropriateness of measurement tools was analyzed by correlation analyses and group comparisons (group 1: 120°–129°, group 2: 130°–139°, group 3: 140°–150°). HFKS showed stronger correlation with knee flexion compared with other scores. While other scores only differentiated between groups 2 and 3, HFKS could differentiate among groups 1, 2 and 3. These findings suggest that employment of proper outcome measurement tool is needed to evaluate and differentiate the knee status in deep flexion range after TKA.