Response to intra-articular cortisone injections in knee osteoarthritis patients with and without effusion on ultrasound: A pilot study.

Objective: Inflammation, manifesting as effusion and synovitis, is thought to contribute to pain in knee osteoarthritis (OA). We conducted a pilot study to investigate recruitment feasibility and assess whether effusion on ultrasound of the knee was associated with greater reduction in knee pain after corticosteroid injection.

Methods: A pilot study was conducted from 2020 to 2021 including patients ≥40 years with knee OA undergoing clinically indicated corticosteroid injections. At baseline, participants completed the Knee Injury and Osteoarthritis Outcome Score (KOOS) Pain subscale and had an ultrasound of the injected knee(s) to assess for effusion, defined as anechoic material in the suprapatellar recess. KOOS Pain was re-assessed two weeks following injection. We used mixed linear models to evaluate the change in KOOS Pain scores for knees with and without effusion to determine estimates of the magnitude of association.

Results: We recruited 10 participants who contributed 16 knees from 4 clinical sessions. The mean age was 68 years (standard deviation [SD] 13) and 90% were female. Six knees had effusion. At baseline, knees without effusion had greater pain (mean KOOS Pain 44, SD 19) compared to those with effusion (mean KOOS Pain 51, SD 15). Knees without effusion had a 6 point (95% CI -16, 28) greater improvement in KOOS Pain 2-weeks post injection compared to those with effusion.

Conclusion: This pilot study demonstrated clinic-based recruitment was feasible. We did not observe clinically important or statistically significant differences in pain relief post corticosteroid injection between knee OA patients with or without effusion.