Researchers in China have found no statistically significant advantage for infrapatellar fat pad glucocorticoid injection over saline for 12-week knee pain change or effusion synovitis volume change in inflammatory knee osteoarthritis.
Osteoarthritis affects approximately 595 million people worldwide, with knee joints identified as the most commonly affected. Symptomatic knee osteoarthritis is linked to physical disability, reduced quality of life, and increased mortality in older adults, while curative drugs remain lacking amid a rising burden tied to aging and obesity.
Some knee osteoarthritis involves inflammation, and inflammation can involve two nearby tissues—the fat pad under the kneecap and the joint lining—that are structurally interconnected and serve as important sources of inflammation in knee osteoarthritis.
Swelling inside a knee with osteoarthritis can be from fluid plus a thickening of the joint lining, a combination called effusion synovitis. Effusion synovitis is reported in more than 46% of people with knee osteoarthritis and links to more knee pain, cartilage defects, bone marrow lesions, cartilage volume loss, and a higher likelihood of joint replacement surgery.
An abnormal fat pad under the kneecap can release inflammatory products associated with changes in cartilage, the joint lining, and the bone beneath cartilage.
Intra-articular glucocorticoid injections are already widely used for pain relief, though there are concerns about cartilage loss. Glucocorticoid injection into the fat pad under the kneecap may offer a way to target inflammation in tissues directly and could potentially provide anti-inflammatory effects while reducing cartilage deterioration risk.
In a study titled “Infrapatellar Fat Pad Glucocorticoid Injection in Knee Osteoarthritis,” published in JAMA Network Open, researchers conducted a randomized, double-blind, placebo-controlled trial to evaluate the effect and safety of glucocorticoid injections into the infrapatellar fat pad in individuals with inflammatory knee osteoarthritis.
Sixty participants entered the trial across four centers in China, with enrollment from April 2022 to June 2023. Follow-up ran 12 weeks, with assessments at baseline and weeks 4, 8, and 12, plus magnetic resonance imaging at baseline and week 12.
Ultrasonography guided a single infrapatellar fat pad injection at baseline, using glucocorticoid for treatment or saline for placebo.
Primary outcomes tracked change in knee pain on a visual analog scale and change in effusion synovitis volume measured by magnetic resonance imaging. The evaluation also included an Osteoarthritis Index score, Hoffa synovitis score, quality of life measurement, pain medication use, infrapatellar fat pad volume, and adverse reactions.
Few changes over 12 weeks
Visual analog scale pain fell over 12 weeks in both groups, though the difference between them did not meet the threshold for statistical significance.
Effusion synovitis volume also declined over 12 weeks, with between-group differences not reaching statistical significance. Osteoarthritis Index scores dropped in both groups over 12 weeks, and also did not reach a difference of statistical significance. Four-dimensional Assessment of Quality of Life scores rose for both groups and again did not reach statistical significance.
Cartilage defect scores did shift significantly in favor of the glucocorticoid group. Adverse reactions appeared once in each group, described as worse pain in the study knee.
Researchers concluded that glucocorticoid injection into the infrapatellar fat pad did not significantly alleviate pain or reduce effusion synovitis volume over 12 weeks in inflammatory knee osteoarthritis.
Follow-up only lasted 12 weeks, leaving structural outcomes such as fat pad atrophy and cartilage loss beyond the study time window. Further investigation was called for to determine the efficacy of this approach.
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Publication details
Yan Zhang et al, Infrapatellar Fat Pad Glucocorticoid Injection in Knee Osteoarthritis, JAMA Network Open (2026). DOI: 10.1001/jamanetworkopen.2025.49938
Journal information:
JAMA Network Open
The content is provided for information purposes only.