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

Background: Approximately 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.
Methods: In 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.
Results: A 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.
Conclusion: Baseline 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.
Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: [Dr. Skou is associate editor of the Journal of Orthopaedic & Sports Physical Therapy and has received personal fees from Munksgaard, TrustMe-Ed and Nestlé Health Science, all of which are unrelated to the submitted work. He is co-founder of Good Life with Osteoarthritis in Denmark (GLA:D®), a not-for-profit initiative hosted at University of Southern Denmark aimed at implementing clinical guidelines for osteoarthritis in clinical practice. The authors declared no other potential conflicts of interest.].
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