Abstract
BackgroundThis study aims to elucidate and compare the relationship between the knee flexion angle and patient-reported outcome measures (PROM) in both non-weight-bearing (NWB) and weight-bearing (WB) conditions.MethodsThis retrospective cohort study included 61 knees (47 patients) who underwent total knee arthroplasty. The knee flexion angle was measured by three conditions: NWB in manual goniometer, NWB in fluoroscopic three-dimensional (3D) analysis and WB in the fluoroscopic 3D analysis. The PROM was evaluated by postoperative 2011 Knee Society Score (2011 KSS) and Knee injury and Osteoarthritis Outcome Score (KOOS). Correlations between the knee flexion angle and PROM was analyzed using Spearman’s correlation coefficient. Additionally, whether the angular difference between NWB and WB correlated with the PROM or not was evaluated.ResultsThe NWB knee flexion angle in a goniometer, NWB in 3D analysis, and WB in 3D analysis were 124.6° ± 8.4°, 118.0° ± 10.5°, and 109.5° ± 13.3°, respectively. The angular difference was 8.5° ± 12.8°. No PROM correlation existed in NWB using a goniometer. Moreover, significant positive correlations in 2011 KSS symptoms (r = 0.35) and 2011 KSS functional activities (r = 0.27) were noted in NWB using 3D analysis. Significant positive correlations existed in 2011 KSS symptoms (r = 0.32), 2011 KSS functional activities (r = 0.57), KOOS pain (r = 0.37), KOOS activity of daily living (ADL; r = 0.45), KOOS sports (r = 0.42), and KOOS quality of life (r = 0.36) in WB using 3D analysis. Significant negative correlations were noted in 2011 KSS functional activities (r = − 0.45), KOOS ADL (r = − 0.30), and KOOS sports (r = − 0.38) in angular difference.ConclusionsThe WB knee flexion angle better correlated with PROM compared with NWB by evaluation of 3D analysis. The larger the angular difference existed between NWB and WB, the lower the PROM score.
Highlights
This study aims to elucidate and compare the relationship between the knee flexion angle and patient-reported outcome measures (PROM) in both non-weight-bearing (NWB) and weight-bearing (WB) conditions
Correlation between the knee flexion angle and PROM In the NWB knee flexion angle using a goniometer, no significant correlation existed between the angle and PROM (Table 3)
The NWB knee flexion angle using 3D measurement correlated with 2011 Knee Society Score (KSS) symptoms and 2011 KSS functional activities, the angle using goniometer measurement did not correlate with PROM at all
Summary
This study aims to elucidate and compare the relationship between the knee flexion angle and patient-reported outcome measures (PROM) in both non-weight-bearing (NWB) and weight-bearing (WB) conditions. Various studies have currently reported the relationship between postoperative knee flexion angle and patientreported outcome measures (PROM). Most of the reports described the positive relationship between knee flexion angle and PROM [2, 5,6,7]. Several reports described the weak or modest relationship between the knee flexion angle and PROM [8,9,10]. The knee flexion angle measurement was performed using the manual goniometer in most studies. The NWB knee flexion angle measurement only may be inadequate to investigate the relationship with PROM. The WB knee flexion angle may reflect the PROM more compared with NWB, and the measurement of knee motion in WB fashion may be a superior method to assess functional capabilities [15]
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