For decades, the medical answer to a worn-out knee joint has been the same: manage pain with anti-inflammatory drugs and physical therapy until the cartilage is gone, then replace the joint with titanium and plastic. That answer — joint replacement surgery, performed more than 700,000 times a year in the United States alone — may be approaching obsolescence. A landmark study published June 12, 2026 in the journal Science by researchers at Stanford Medicine demonstrates that a single injection blocking a protein linked to aging can not only stop the progression of arthritis but actively reverse cartilage loss that had already occurred — and that human cartilage tissue responds to the same treatment.
The findings, led by Dr. Helen Blau, director of the Baxter Laboratory for Stem Cell Biology at Stanford University School of Medicine, and Dr. Nidhi Bhutani, professor of orthopedic surgery, center on a single enzyme: 15-hydroxy prostaglandin dehydrogenase, known as 15-PGDH. This enzyme — which increases with age in multiple tissues and which the research team previously identified as a key driver of tissue decline in older organisms — acts as a biological brake on the body's ability to regenerate cartilage. As 15-PGDH accumulates in aging cartilage tissue, it progressively disables the chondrocytes (cartilage-producing cells) that would normally maintain and repair the joint surface.
