Range of movement correlates with the Oxford knee score after total knee replacement: A prediction model and validation

• Published in: The knee Vol. 23; no. 3; pp. 511 - 516
• Main Authors: Maempel, Julian F, Clement, Nicholas D, Brenkel, Ivan J, Walmsley, Phil J
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.06.2016; Elsevier Limited
• Subjects: Age; Arthroplasty, Replacement, Knee; Body mass index; Confidence intervals; Gender; Health Status Indicators; Humans; Joint surgery; Models, Theoretical; Orthopedics; Osteoarthritis, Knee - surgery; Oxford knee score; Pain; Patient Reported Outcome Measures; Patient satisfaction; Prognosis; Range of motion; Range of Motion, Articular; Regression analysis; Reproducibility of Results; Total knee replacement; Treatment Outcome; Variables; United Kingdom > UK; Total knee replacement; Range of motion; Oxford knee score
• ISSN: 0968-0160; 1873-5800
• DOI: 10.1016/j.knee.2016.01.009

Abstract Background Patient reported outcome measures are widely used in the evaluation of outcomes after Total Knee Replacement (TKR) in joint registries and large studies. The aim of this study was to assess the relationship between the Oxford knee score (OKS) and range of motion (ROM) after TKR, and to construct and validate prediction models of ROM from the measured OKS. Methods Eight hundred sixty patients reviewed five years postoperatively and 273 patients reviewed nine to 10 years postoperatively completed an OKS. Of these, 808 (94%) and 226 (83%) patients, respectively, had a complete dataset (knee extension and ROM) and formed the study cohort. Results Regression analysis demonstrated a significant correlation between the OKS and ROM (r = 0.38, p < 0.001) after adjusting for other confounding variables (age, sex, body mass index, and knee extension). A prediction model was constructed and validated using a second cohort of 226 patients at nine to 10 years after their TKR. Intraclass correlation demonstrated good reliability (r = 0.60, 95% CI 0.47 to 0.69) between predicted and actual measured ROM for this group. However, when the OKS is used in isolation the reliability of the predicted ROM is diminished (intraclass correlation r = 0.41, 95% CI 0.24 to 0.55). Conclusions The OKS is an independent predictor of ROM after TKR. It is also possible to predict ROM from the OKS, but the reliability of this is improved when other independent predictors such as age, gender, body mass index (BMI) and degree of knee extension are also acknowledged.