More Severe Radiographic Osteoarthritis Is Associated With Increased Improvement in Patients’ Health State Following a Total Knee Arthroplasty

BACKGROUND: To assess whether preoperative radiological severity of osteoarthritis (OA) is related to the level of improvement in patients' health state measured 1 year after total knee arthroplasty (TKA). METHODS: Radiographic severity of OA was graded using the Kellgren-Lawrence (KL) classification. Two independent observers were blinded to patients' outcome scores. Health-related quality of life was measured using EQ-5D-3L preoperatively and at 12-month follow-up. The 5 dimensions of the EQ-5D were converted into a health state index score. The association between KL grade and improvement in health state score was analyzed using multiple linear regression. RESULTS: Among 156 consecutive patients (68% females, mean age 69 years) who underwent primary TKA, 3 knees (2%) were classified as KL grade 2, 115 as KL grade 3 (74%), and 38 as KL grade 4 (24%). Follow-up rate was 77%. There was substantial intra-rater and inter-rater agreement (Cohen's kappa = 0.80 and 0.79). Most patients (64%) had clinically significant improvement in their health state score 1 year after TKA. However, after adjusting for relevant covariates, patients with severe OA (KL grade 4) were found to have significantly more improvement in their health state score than patients with mild or moderate OA (KL grade 2 or 3, respectively). Separate analysis of the 5 EQ-5D dimensions showed that the KL group differences were most evident in the "usual activities" and "pain/discomfort" dimensions. CONCLUSION: Patients with severe OA have significantly more improvement in their usual activities and pain/discomfort 1 year after TKA than patients with less severe OA.