To determine whether changes in preoperative osteoarthritis (OA) symptoms are associated with improvement after total knee replacement (TKR) and to identify predictors of clinically significant improvement.
Data on Osteoarthritis Initiative participants who were annually assessed and underwent TKR were included. T0 was the assessment prior to TKR while T-1 was the assessment prior to that. T+2 was the second assessment after TKR. We compiled data on the Western Ontario and McMaster Universities OA Index (WOMAC), OA-related symptoms, and radiographic severity. We defined clinically significant improvement as improvement in WOMAC total score ≥ to the minimal important difference (MID) (0.5 SD of mean change) between T0 and T+2 and also considered other definitions of improvement. Logistic regression models were performed to evaluate the relationship between improvement and preoperative measures.
Improved (n = 211) compared to unimproved (n = 58) patients had greater worsening of their WOMAC pain (p = 0.002) and disability (p < 0.001) from T-1 to T0. Preoperative measures as predictors of improvement included higher WOMAC disability (OR = 1.08, p < 0.001), presence of chronic OA symptoms in the surgical knee (OR = 5.77, p = 0.033), absence of OA-related symptoms in the contralateral knee (OR = 9.25, p < 0.001), exposure to frequent knee bending (OR = 3.46, p = 0.040), and having a Kellgren-Lawrence x-ray grade of ≥2 in the contralateral knee (OR = 4.71, p = 0.010).
More than 75% of participants had improvement after TKR. Improved patients were more likely to have escalation of OA pain and disability prior to surgery than unimproved patients. Other preoperative measures predicted improvement after TKR.