The Role of Early Range of Motion in Predicting Long-Term Outcomes in Total Knee Arthroplasty

Introduction Knee stiffness is a potential complication following total knee arthroplasty (TKA). It is possible that early post-operative range of motion (ROM) can predict longer-term outcomes, which can be used to optimise clinical care during recovery. This study aimed to investigate whether early post-operative ROM can predict longer-term ROM and patient-reported outcome measures (PROMs) following TKA. Methods Analysis utilised prospectively collected data from 278 patients who underwent a robotic-assisted TKA. A linear regression model was applied using SPSS to assess whether early ROM could predict knee ROM and PROMs at two years follow-up. Early ROM was assessed pre-operatively, prior to hospital discharge, and at 6 weeks post-surgery. Multivariate analysis was conducted to explore the influence of patient demographics (age, sex, ethnicity, body mass index (BMI), and American Society of Anesthesiologists (ASA) status) on long-term ROM and PROMs, including the Oxford Knee Score (OKS), Forgotten Joint Score (FJS), International Knee Society Scoring (IKSS), and visual analogue scale (VAS). Results The mean pre-operative ROM was 124°, compared with 119° at 2 years. Six patients required manipulation under anaesthesia. Pre-operative and early knee ROM showed a weak predictive relationship with 2-year post-operative knee ROM (pre-operative: B = 0.244, p < 0.001; discharge: B = 0.097, p = 0.002; 6-week post-operative: B = 0.255, p < 0.001). The magnitude of these relationships was small. No relationship was observed between early knee ROM and long-term PROMs. Demographic factors did not impact on long-term ROM or PROMs at the 2-year follow-up. Conclusion The findings of this study suggest that while early ROM may have a weak positive association with long-term ROM, it is not a reliable predictor of long-term PROMs following TKA. A reduced ROM in the initial post-operative period should not cause concern for patients and clinicians and should not delay timely discharge from hospital.