Oxford knee score 1 year after TKR for osteoarthritis with reference to a normative population: What can patients expect?

Objectives: Total knee replacement (TKR) procedure is commonly carried out in patients with advanced osteoarthritis to reduce pain and increase mobility, with on average 84% rated satisfactory outcome, but some (some suggest 44%) continue to experience debilitating pain. The study aimed to investigate factors affecting pain and function outcomes (using Oxford Knee Score, OKS) one year after TKR, with normative comparison to a reference population. Design: We recruited TKR patients from one hospital (Nottinghamshire, UK); collected pre- and post-operative OKS; graded radiographs for severity of osteoarthritis (K-L grade) in a sub-group. We also collected OKS by postal survey from the local area, calculated age and sex specific normative scores and z-scores of post-operative OKS (Z-OKS). The associations between K-L grade, pre-operative OKS, age, sex, against change in OKS and Z-OKS were analysed. Results: There were 536 TKR cases, 91 in radiographic sub-group and 360 people in reference cohort. Post-operative Z-OKS was associated with K-L grade (β ​= ​0.368; p<0.001). Change in OKS was associated with K-L grade (β ​= ​0.247; p ​= ​0.003); pre-operative OKS (β ​= ​-0.449; p<0.001); age (β ​= ​0.276; p ​= ​0.001); and female sex protective (β ​= ​-0.213; p ​= ​0.008). On average TKR patients returned to 74% of their normative age and sex adjusted OKS, with younger women achieving worst outcomes. More severe radiographic osteoarthritis predicted greater improvement and better post-operative outcome when compared to normative population. Conclusion: This study identified factors and provided normative OKS data intended to guide clinicians in counselling patients regarding likely surgical outcomes. This could help manage patients' expectations, aid decision making and increase post-surgery satisfaction rate.