Platelet-rich plasma, or PRP, is a substance that’s thought to promote healing when injected. Plasma is a component of your blood that contains special “factors,” or proteins, that help your blood to clot. It also contains proteins that support cell growth. Researchers have produced PRP by isolating plasma from blood and concentrating it.

The idea is that injecting PRP into damaged tissues will stimulate your body to grow new, healthy cells and promote healing. Because the tissue growth factors are more concentrated in the prepared growth injections, researchers think the body’s tissues may heal faster.

The treatment hasn’t been definitively proven. It also hasn’t been approved as a treatment by the U.S. Food and Drug Administration. However, famous athletes like Tiger Woods and tennis star Rafael Nadal have been known to use these injections to help heal injuries.