Knee Fat Pad Steroid Injections Miss the Mark in Inflammatory Osteoarthritis Trial
A 60-patient RCT found infrapatellar fat pad glucocorticoid injections failed to significantly reduce knee pain or effusion vs placebo over 12 weeks.
Summary
The GLITTERS trial randomized 60 adults with inflammatory knee osteoarthritis to glucocorticoid or saline injections into the infrapatellar fat pad (IPFP), with both groups also receiving hyaluronic acid. Over 12 weeks, the glucocorticoid group reduced VAS pain by 39.3 mm versus 31.4 mm in placebo—a non-significant difference. Effusion synovitis volume declined similarly in both groups. Post hoc analyses suggested steroid recipients had greater WOMAC pain reduction and less cartilage deterioration, but these findings were exploratory. The trial concluded that IPFP glucocorticoid injections did not meaningfully outperform placebo for the primary endpoints, highlighting the need for better-targeted anti-inflammatory strategies in this OA subtype.
Detailed Summary
Knee osteoarthritis (OA) affects roughly 595 million people globally and carries a mounting burden with aging populations and rising obesity rates. A prominent OA subtype—inflammatory knee OA—is characterized by activation of the infrapatellar fat pad (IPFP) and synovium, which together release pro-inflammatory mediators that accelerate cartilage, synovial, and subchondral bone damage. MRI-detected signal changes in the IPFP (Hoffa synovitis) and effusion synovitis are each independently linked to pain severity and structural decline. While intra-articular glucocorticoid injections are an established short-term pain option, evidence from at least one RCT indicates they may accelerate cartilage loss—prompting interest in injecting directly into the IPFP as a way to deliver anti-inflammatory effects while minimizing chondrocyte exposure.
The GLITTERS trial was a 12-week multicenter, randomized, double-blind, placebo-controlled study conducted at four Chinese centers. Between April 2022 and June 2023, 141 patients were screened and 60 enrolled. All participants were aged 45 or older, had symptomatic knee OA per ACR criteria, persistent pain ≥6 months, VAS ≥40 mm, Hoffa synovitis score ≥1, and effusion synovitis score ≥1 (combined ≥3). The treatment arm (n=30) received ultrasound-guided IPFP injections of glucocorticoid plus hyaluronic acid; the placebo arm (n=30) received saline plus hyaluronic acid. The primary outcomes were VAS pain change and MRI-measured effusion synovitis volume change at 12 weeks. Secondary outcomes included WOMAC total score, Hoffa synovitis score, quality of life (AQoL-4D), pain medication use, IPFP volume, and adverse events.
All 60 participants (mean age 65 years; 63% women) completed the trial. The glucocorticoid group reduced VAS pain by 39.3 mm versus 31.4 mm in placebo (between-group difference −7.9 mm; 95% CI, −19.7 to 4.0 mm; not statistically significant). Effusion volume declined by 4.9 mL versus 5.4 mL, respectively, also non-significant. Neither Hoffa synovitis score nor IPFP volume differed significantly between arms. In post hoc analyses, the treatment group showed a significantly greater reduction in WOMAC pain (−113.0 vs −66.8 points; difference −46.2 points; P=.04) and a favorable trend in cartilage defect scores (−0.1 vs +0.4; difference −0.5; P=.03), suggesting possible structural and functional benefits that warrant hypothesis-driven follow-up. Adverse events were minimal and balanced (one event per group).
These findings indicate that directing glucocorticoid into the IPFP rather than the joint space does not produce a clinically meaningful advantage over placebo injections with hyaluronic acid background for the primary endpoints of pain and effusion. The rationale—targeting perisynovial adipose inflammation to spare cartilage—remains biologically compelling, but may require different agents, dosing schedules, or patient selection strategies. The post hoc cartilage defect finding is intriguing and could inform future trials designed with structural outcomes as a primary endpoint.
Key caveats limit interpretation: the trial enrolled only 60 participants (possibly underpowered for detecting modest effect sizes), the 12-week follow-up may be too short to capture structural benefits, and post hoc findings should not be over-interpreted. Nonetheless, this is the first RCT to test intra-IPFP glucocorticoid injection and provides an important negative result to guide the field toward more precise phenotype-matched interventions in inflammatory knee OA.
Key Findings
- IPFP glucocorticoid injections reduced VAS pain by 39.3 mm vs 31.4 mm for placebo—not a statistically significant difference.
- Effusion synovitis volume fell similarly in both groups (~5 mL), with no significant between-group difference at 12 weeks.
- Post hoc analysis showed significantly greater WOMAC pain reduction in the glucocorticoid group (−113 vs −67 points; P=.04).
- Cartilage defect scores improved in the glucocorticoid group and worsened slightly in placebo (P=.03, post hoc).
- Adverse events were rare and equal (one per group), suggesting the procedure is safe but not clearly effective.
Methodology
Twelve-week multicenter double-blind RCT (n=60) at four Chinese centers; participants required MRI-confirmed Hoffa synovitis and effusion synovitis. Ultrasound-guided IPFP injections of glucocorticoid vs saline, both with hyaluronic acid background; primary outcomes assessed by VAS pain and MRI-quantified effusion volume at week 12.
Study Limitations
The sample size of 60 is small and likely underpowered to detect modest treatment effects, and the 12-week follow-up is short for detecting structural changes. Background hyaluronic acid in both arms may have obscured between-group differences, and post hoc subgroup findings must be interpreted cautiously.
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