Coronal tibiofemoral subluxation is not an independent risk factor for total knee arthroplasty in patients with moderate to severe varus-osteoarthritis: data from the "Osteoarthritis Initiative"

Only few prognostic factors for progression of knee osteoarthritis are well established, including varus malalignment. The purpose of this study was to evaluate whether coronal tibiofemoral subluxation is a predictor for total knee arthroplasty. Patients from the progression subcohort of the longitudinal database "Osteoarthritis Initiative" with moderate to severe osteoarthritis and varus malalignment of greater than 3 degrees were included. Patients who underwent total knee arthroplasty were matched with patients treated conservatively. Subluxation was measured on full limb length X-rays. Cox regression analysis was performed to retrospectively evaluate subluxation as a risk factor for total knee arthroplasty and check for a possible association between subluxation and pain at the beginning of the observation period in this study. A total of 215 patients were included. Cox regression demonstrated that varus malalignment increased the hazard to undergo surgery by 16% (HR 1.158, p = 0.008) while subluxation did not (HR 1.12, p = 0.11). Furthermore, subluxation was neither associated with poor WOMAC (OR 1.13, p = 0.194) nor KOOS (OR 1.11, p = 0.256) knee pain scores at the beginning of the observation period. The results presented show that subluxation is neither an independent risk factor for total knee arthroplasty, nor for poor pain scores. III.