Prognostic factors of knee pain and function 12 months after total knee arthroplasty: A prospective cohort study of 798 patients

Abstract

BackgroundApproximately 20% of patients undergoing total knee arthroplasty (TKA) do not experience long-term improvements. Our aim was to identify prognostic factors of knee pain and function 12 months after TKA. MethodsIn a prospective cohort study, 1026 patients underwent primary TKA between 2018 and 2020. Main outcome was measured by the Oxford Knee Score (OKS) categorized in five categories (0–9, 10–19, 20–29, 30–39 and 40–48). Potential prognostic factors obtained at baseline included sex, age, baseline OKS, pain catastrophizing scale, EuroQol 5 dimensions, previous surgery, BMI, ASA classification, opioid consumption, living and employment conditions as well as educational level. Ordinal logistic regression analysis was used to identify prognostic factors of OKS. ResultsA total of 915 patients completed follow up (89%), and patients with complete data were included (n = 798). Patients with a baseline OKS between 10–19 and 20–29 had 2.5 (CI 1.6;4.0) and 1.6 (CI 1.1;2.4) higher odds, respectively, of no improvement or deterioration to a lower post-operative OKS category, compared with patients with a baseline score between 30 and 39. Female patients had 1.5 (CI 1.1;2.0) and patients receiving social benefits compared with retired patients had 2.0 (CI 1.1;3.5) higher odds of no improvement or deterioration to a lower OKS category. ConclusionBaseline level of pain and function, sex and employment status were significant prognostic factors of OKS 12 months after TKA. Overall, the regression analysis only explained 4% of the outcome, indicating that it is difficult to predict 12-month TKA outcome prior to surgery.