GLP-1 triple agonist retatrutide delivers dramatic pain relief and weight loss in knee osteoarthritis

A new class of obesity drug may be about to reshape how doctors treat knee osteoarthritis (OA). Data from the phase 3 TRIUMPH-4 trial, presented at ACR Convergence 2026 and simultaneously published in the New England Journal of Medicine, show that retatrutide — Eli Lilly's triple-receptor agonist targeting GIP, GLP-1, and glucagon — dramatically reduced knee OA pain and improved physical function in patients with obesity over 68 weeks.

The trial randomized 445 patients to retatrutide 9 mg, 12 mg, or placebo weekly. Both active doses cut WOMAC pain scores by more than 4.4 points versus 2.43 points with placebo — a clinically meaningful difference. Notably, about 70% of retatrutide-treated patients achieved a 70% reduction in pain, compared to just 26% on placebo. These results build on the earlier TRIUMPH-1 trial (n=2,339), which showed up to 25% mean weight loss and a 61.6% reduction in OA pain at 80 weeks.

By the Numbers:

• ~26–29% mean body weight reduction with retatrutide vs. ~2% with placebo
• WOMAC pain score drop: –4.48 (9 mg) and –4.41 (12 mg) vs. –2.43 (placebo)
• ~70% of retatrutide patients achieved ≥70% pain reduction vs. 26% on placebo
• 13–18% of retatrutide patients withdrew due to adverse events vs. 4% on placebo

Why it matters: No FDA-approved GLP-1 therapy currently exists for knee OA pain — but these results could change that. With new ACR guidelines already emphasizing weight loss in OA management, retatrutide may represent a meaningful treatment option for the millions of patients living with obesity-related joint disease.