To determine whether clinical correlates of knee osteoarthritis (OA) affect the outcome of intraarticular steroid injections (IASI) in symptomatic knee OA.
Men and women aged ≥ 40 years with painful knee OA who participated in an open-label trial of IASI completed questionnaires and clinical examination. The Outcome Measures in Rheumatology (OMERACT)-Osteoarthritis Research Society International (OARSI) criteria were used to assess response to therapy in the short term (within 2 weeks). Among those who initially responded, those whose pain had not returned to within 20% of the baseline Knee Injury and Osteoarthritis Outcome Score pain score at 6 months were characterized as longer-term responders. Log-binomial regression was used to examine factors associated with outcome.
One hundred ninety-nine participants were included, of whom 146 (73.4%) were short-term and 40 (20.1%) longer-term responders. Compared to short-term nonresponders, participants with these characteristics were more likely to be short-term responders: medial joint line tenderness [relative risk (RR) 1.42, 95% CI 1.10-1.82], medial and lateral joint line tenderness (RR 1.38, 95% CI 1.03-1.84), patellofemoral tenderness (RR 1.27, 95% CI 1.04-1.55), anserine tenderness (RR 1.27, 95% CI 1.06-1.52), and a belief that treatment would be effective [RR/unit increase (range 0-10) = 1.05 (1.01-1.09)]. Aspiration of joint fluid (RR 0.79, 95% CI 0.66-0.95) and previous ligament/meniscus injury (RR 0.63, 95% CI 0.44-0.91) were associated with a reduced risk of being a short-term responder. Compared to initial nonresponders and those whose pain recurred within 6 months, participants with a higher number of pain sites [RR/unit increase (range 0-10) = 0.83, 95% CI 0.72-0.97], chronic widespread pain (RR 0.32, 95% CI 0.10-0.98), perceived chronicity of disease [RR/unit increase (range 0-10) = 0.86, 95% CI 0.78-0.94], and a higher depression score [RR/unit increase (range 0-21) = 0.89, 95% CI 0.81-0.99] were less likely to be longer-term responders.
Among patients with symptomatic knee OA, tenderness around the knee was associated with better short-term outcome of IASI. However, clinical-related factors did not predict longer-term response, while those with chronic widespread pain and depressive symptoms were less likely to obtain longer-term benefits.