Extent of Tibiofemoral Osteoarthritis Before Knee Arthroplasty: Multicenter Data from the Osteoarthritis Initiative

Knee arthroplasty traditionally is recommended for persons with substantial disability and disabling pain attributable to moderate or severe osteoarthritis (OA). Pain and functional status after arthroplasty may be influenced by the extent of knee OA before surgery and recent evidence suggests persons with less severe knee OA before undergoing TKA have greater pain levels and worse function than persons with more severe knee OA. We determined the proportion of patients undergoing knee arthroplasty who had less than moderate knee OA before surgery and who had either a radiographically normal medial or lateral joint space before surgery. One hundred sixteen persons in the Osteoarthritis Initiative underwent knee arthroplasty during a 3-year period. Ninety-seven of the 116 patients (84%) had radiographs available less than 1 year before surgery and were included. We used Z-tests to determine whether the proportion of patients with a modified Kellgren-Lawrence (KL) grade of 3 or higher differed from literature-based estimates. In addition, we described the proportion of patients with medial and lateral joint space narrowing. The proportion of patients with a modified KL grade of 3 or higher was 0.81 (95% CI, 0.73-0.89) and was less than the 0.95 estimated population proportion. Of the patients who underwent knee arthroplasty, 85% (82 of 97 knee arthroplasties) had at least one tibiofemoral joint compartment that had no joint space narrowing. One in six patients with OA who underwent knee arthroplasty had a KL grade of 2 or lower. Variation in the extent of tibiofemoral OA in patients preparing for joint arthroplasty is greater than previously described. A greater percentage of patients undergoing knee arthroplasty may be at risk for increased pain and poorer function than previously assumed after surgery because of less severe knee OA before surgery. Level I, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.