If knee pain, stiffness, or cracking joints are becoming part of daily life, new research offers hope. Researchers at Stanford University have discovered a drug that can stimulate the regrowth of knee cartilage—something long believed to be impossible without surgical intervention.

The findings, published in the journal Science, focus on a protein called 15-PGDH, which increases with age in knee cartilage. This protein breaks down prostaglandin E2, a molecule essential for keeping cartilage healthy and capable of self-repair. As levels of 15-PGDH rise, the joint’s natural healing ability is suppressed, accelerating cartilage loss and arthritis.

By blocking 15-PGDH in older mice, researchers observed a remarkable effect: cartilage didn’t just stop deteriorating—it grew back. The joint surface became thicker, mobility improved, and repair occurred without surgery, stem cells, or implants. Instead, existing cartilage cells were effectively “rejuvenated,” behaving like younger, healthier cells.

The team then tested the drug on human knee cartilage obtained from patients undergoing knee replacement surgery. After just one week of treatment, the tissue showed signs of new cartilage formation and reduced damage. According to study co-author Nidhi Bhutani, the regenerative response was stronger than with any previous drug tested.

In another experiment, mice with ligament injuries similar to ACL tears received injections over four weeks. These mice did not develop arthritis, unlike untreated ones—suggesting the drug may also prevent post-injury arthritis.

The drug is currently in Phase 1 clinical trials for age-related muscle weakness. The technology has been licensed to Epirium Bio, co-founded by lead researcher Helen Blau, which plans to begin cartilage- and arthritis-focused trials next.

If human trials are successful, this treatment could transform arthritis care—offering millions a non-surgical way to preserve joint health and potentially delaying or avoiding knee replacement surgery altogether.