Autologous Platelet-rich Plasma Therapy for Knee Osteoarthritis

Conservative treatments for knee osteoarthritis (OA) focus on relieving symptoms such as joint pain and inflammation. However, autologous platelet-rich plasma (PRP) therapy has been proposed and offered by some clinicians as a new conservative treatment for knee OA. The treatment is intended to slow or halt the progressive degeneration of articular (i.e., joint) cartilage by using autologous (i.e., patient-derived) platelets—a component of blood plasma—injected into arthritic joints.1 Platelets secrete a number of growth factors that some clinical researchers believe can promote tissue repair and regeneration.1,2 Thus, some researchers have postulated that PRP therapy has potential to halt or reverse the cartilage degeneration that characterizes OA, rather than just temporarily relieve symptoms, by repairing and regenerating damaged cartilage, although the precise mechanism of action is not well understood.2,3

In a typical autologous PRP procedure, clinicians first collect about 50 mL of a patient's blood and then process it in a centrifuge to obtain a concentrated volume of platelets in about 5 mL of plasma.1,2,4 In ongoing and published clinical trials of PRP to treat knee OA, physicians injected the prepared platelets directly into the affected joint under ultrasound guidance, with a series of injections administered over several weeks. Each injection generally requires a separate blood collection and processing procedure performed during the same patient visit.5,6 Over the past decade, physicians have also used PRP therapy for soft-tissue injuries, including chronic wounds and tendonitis.3

The U.S. Food and Drug Administration (FDA) does not subject autologous PRP to the same type of marketing approval requirements associated with drugs and devices. Autologous PRP may be included in the category of human cells, tissues, and cellular and tissue-based products removed from an individual and reimplanted in the same individual during a single surgical procedure, thereby making the procedure exempt from FDA licensure requirements.7 However, PRP products would be subject to FDA standards for safe collection and processing of blood and blood products, including PRP.8 FDA has granted marketing clearance for...