Infrapatellar Fat Pad Glucocorticoid Injection in Knee Osteoarthritis

Importance: Intra-articular glucocorticoid injections are widely used to alleviate knee osteoarthritis (OA) pain, but evidence suggests these injections may cause cartilage loss. The infrapatellar fat pad (IPFP) and synovium are important sources of inflammation in knee OA; injecting glucocorticoid into the IPFP may not only provide anti-inflammatory effects but also reduce cartilage deterioration in patients with inflammatory knee OA. Objective: To evaluate the effect and safety of glucocorticoid injections into the IPFP in individuals with inflammatory knee OA. Design, Setting, and Participants: This randomized, double-blind, placebo-controlled trial included patients aged 45 years and older with inflammatory knee OA at 4 centers in China. Patients were enrolled from April 2022 to June 2023. Intervention: Patients were randomly assigned to the treatment group (n = 30) or placebo group (n = 30). Each group received either glucocorticoid or saline injections into the IPFP with hyaluronic acid as background treatment under ultrasonographic guidance. Main Outcomes and Measures: The primary outcomes were changes in knee pain on a visual analog scale (VAS) and effusion synovitis volume measured by magnetic resonance imaging (MRI). Secondary outcomes included changes in the total score of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), MRI-detected Hoffa synovitis score, quality of life assessed using the 4-dimensional Assessment of Quality of Life, pain medication use, IPFP volume, and the incidence of adverse reactions. Outcomes were assessed over 12 weeks. Results: All 60 participants (mean [SD] age, 65 [11] years; 38 [63%] women) completed the study. The treatment group compared with the placebo group did not have a statistically significant reduction in VAS pain (-39.3 mm vs -31.4 mm; between-group difference, -7.9 mm; 95% CI, -19.7 to 4.0 mm). There was no significant between-group difference in effusion volume reduction (-4.9 mL vs -5.4 mL; between-group difference, 0.5 mL; 95% CI, -1.9 to 2.9 mL). In post hoc analyses, the treatment group had significantly greater reduction in the WOMAC pain score (-113.0 points vs -66.8 points; between group difference, -46.2 points; 95% CI, -90.0 to -2.4 points; P = .04) and cartilage defect (-0.1 vs 0.4; between-group difference, -0.5; 95% CI, -1.0 to -0.1; P = .03). Both groups had 1 participant who experienced 1 adverse reaction. Conclusions and Relevance: In this randomized clinical trial, glucocorticoid injections into the IPFP did not effectively alleviate knee pain or reduce effusion synovitis volume in inflammatory knee OA. Further investigation is needed to determine the efficacy of this treatment approach. Trial Registration: ClinicalTrials.gov Identifier: NCT05291650.