Platelet-rich plasma (PRP) therapy, in which a few tablespoons of blood are removed from a patient with a soft-tissue injury, spun in a centrifuge, and injected directly into the injury, has made headlines in the past year as top athletes such as Hines Ward and Tiger Woods have turned to the blood treatment for quick recoveries from injuries. When the patient's blood is run through the centrifuge, it leaves a highly concentrated sample of platelets, which contain proteins known as growth factors. These proteins promote cell growth, and when injected into the site of an injury, are thought to speed the healing process.

The use of PRP therapy dates back almost 20 years, when Spanish dental surgeons began using the technique to help improve the healing time of bone graft procedures for dental implants. Since then PRP therapy has been used in many areas, but most recently it has experienced a surge in popularity in the field of sports medicine and arthroscopy. Pittsburgh Steelers receiver Hines Ward was able to play in the 2009 Super Bowl just two weeks after suffering a sprained medial collateral ligament in his right knee, thanks to PRP therapy. Tiger Woods also reportedly underwent the treatment in 2009 while recovering from knee surgery. Since then, many other professional and amateur athletes have sought out this treatment so they too can get back in the game quickly.

With so many patients seeking out PRP therapy, dozens of studies have been conducted to determine how effective the treatment is. In January of this year, JAMA published an article citing a Dutch study of patients with chronic Achilles tendinopathy, which found that PRP therapy was no better than placebo. Just a month later the Journal of Arthroscopy ran a review article citing other studies that contradicted the Dutch study. In March four new studies were presented at the AAOS annual meeting with three showing promising results for the use of PRP therapy for knee injuries, chronic tennis elbow, and chronic Achilles tendinitis, while the fourth found no significant effect for pain management in arthroscopic rotator cuff repair.

More studies are still underway, measuring the effectiveness of PRP for every possible type of injury. There is another layer to the PRP debate which may explain some of the different study results thus far. Currently there is no exact established protocol for how to use PRP therapy. From how often to have the injections to whether or not to add calcium to the platelets, the delivery of PRP is as controversial as its effectiveness.