Infrapatellar Fat Pad Glucocorticoid Injection in Knee Osteoarthritis

1. Infrapatellar fat pad (IPFP) glucocorticoid injections do not significantly reduce pain or effusion volume compared to placebo in knee osteoarthritis (OA).

Evidence Rating Level: 1 (Excellent)

Study Rundown: Osteoarthritis is a debilitating condition that leads to physical disability, reduces quality of life, and most commonly affects the knee joint. Intra-articular glucocorticoid injections are reserved for patients when other pharmacological treatments are ineffective. However, they provide pain relief for weeks to months, with a decreasing magnitude of pain relief over this time. Furthermore, glucocorticoid injections may induce cartilage loss. Studies have shown that IPFP alterations may play a critical role in knee OA, particularly in patients with comorbid effusion synovitis and Hoffa synovitis. Therefore, there is a need to evaluate if IPFP glucocorticoid injections effectively alleviate knee pain.

This 12-week randomized, double-blind, placebo-controlled trial was conducted across 4 centres in China from April 2022 to June 2023. Participants included adults aged 45 years or older who met the symptomatic knee OA criteria according to the American College of Rheumatology standards and had positive Hoffa and effusion synovitis scores. Patients randomized to the glucocorticoid group received one IPFP injection of 1 mL of glucocorticoid (containing 5 mg of betamethasone dipropionate and 2 mg of betamethasone sodium phosphate), 0.5 mL lidocaine, and 0.5 mL saline. Patients randomized to the placebo group received one IPFP injection of 0.5 mL lidocaine and 1.5 mL saline. Patients in both groups received concomitant intra-articular injections of 2.5 mL hyaluronic acid (containing 25 mg of sodium hyaluronate).

Overall, this study found that there were no statistically significant differences in the reduction of pain or effusion volume between the glucocorticoid and placebo groups. Post-hoc analyses showed the treatment group had significantly greater reduction in Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain score and cartilage defect. Adverse events were rare in both groups. Further studies are required to compare the effectiveness of IPFP versus intra-articular glucocorticoid injections.

Click here to read this study in JAMA Network Open

Relevant reading: Association between knee inflammation and knee pain in patients with knee osteoarthritis: a systematic review

In-depth [randomized clinical trial]: Intra-articular glucocorticoid injections are widely used in the management of knee OA. IPFP has been implicated in OA pathogenesis. This randomized controlled trial investigated the efficacy and safety of IPFP glucocorticoid injection with intra-articular hyaluronic acid compared to intra-articular hyaluronic acid alone. The primary outcomes were changes in knee pain and effusion synovitis volume.

60 patients were randomized in a 1:1 ratio to the glucocorticoid and placebo arms (mean [SD] age, 64.9 [11.1] years; 63.3% female). After 12 weeks, the treatment and placebo groups had reductions in visual analogue scale (VAS) pain scores of 39.3 (95% CI, 27.5 to 51.1) and 31.4 (95% CI, 19.7 to 43.1) points, resulting in a non-significant between-group difference of −7.9 points (95% CI, −19.7 to 4.0 points). The most significant VAS decrease occurred after 4 weeks. There was no significant 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). Between-group differences in Hoffa synovitis scores (−0.1 (95% CI, −0.3 to 0.2) were non-significant. Post hoc analyses showed IPFP glucocorticoid injection statistically reduced WOMAC pain scores (between-group difference of –46.2 (95% CI, –90.0 to –2.4)). 10.0% and 23.3% of patients in the treatment and placebo groups experienced at least one adverse event.

Image: PD

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