Researchers at Stanford Medicine report that blocking a protein linked to aging can restore cartilage that naturally wears away in the knees of older mice. In the study, the injectable treatment not only rebuilt cartilage but also stopped arthritis from developing after knee injuries similar to ACL tears, which are common among athletes and active adults. A pill-based version of the same therapy is already being tested in clinical trials aimed at treating muscle weakness associated with aging.

Human knee tissue collected during joint replacement surgeries also responded positively to the treatment. These samples, which include both the joint’s supporting extracellular scaffolding, or matrix, and cartilage-producing chondrocyte cells, began forming new cartilage that functioned normally.

Together, these findings point to the possibility that cartilage lost through aging or arthritis could one day be restored using a localized injection or an oral medication, potentially eliminating the need for knee or hip replacement surgery.