MINNEAPOLIS On December 10, 2011, Portland guard Brandon Roy announced his retirement. He was 27 years old at the time, at the end of just his fifth year in the league. He'd been the NBA Rookie of the Year in 2007 and was a three-time All-Star.

Yet in the face of chronic knee problems, none of that mattered.

Roy retired due to persistent issues in both of his knees. He'd undergone six knee operations, and there was no longer any cartilage remaining in the joints. Trail Blazers team doctors warned him that he should not continue playing and that to do so would have devastating long-term effects.

Not even a year later, and he's announced his comeback. Many teams have expressed interest in signing him, including the Timberwolves.

That's quite the turnaround for a player who was warned that to play basketball any longer might spell difficulties walking later in his life. It's the kind of story where one wonders what detail is missing; the turnaround is too drastic. And in that brief narrative, something was missing: platelet-rich plasma (PRP) therapy.

PRP therapy is a process by which a small quantity of blood is extracted from a patient. The blood is then placed in a centrifuge and spun until it separates into its component parts. Doctors then remove the platelets and inject them back into the patient at the point of injury, peppering the surrounding area with injections for maximum efficacy. The growth factors in platelets are said to promote healing and tissue regeneration, speeding the healing process.

The therapy has been used for nearly a decade, but it's received increased attention in recent years. There's no medical consensus on it yet, and it's still a procedure that's largely relegated to athletes and patients with disposable income. It can cost between $500-$2,000, though prices do vary, and it's rarely covered by insurance.

Dr. Bradley Nelson, a physician at the University of Minnesota School of Medicine, said that the most common use of PRP therapy is for chronic tendinopathy. That's different from the case in Roy's knees, where he's lacking cartilage. Using PRP therapy cases like Roy's, though, is becoming more widespread, but it doesn't have the same healing effects as it does in treating tendinopathy, such as tennis elbow. Recent studies have begun to indicate that PRP can be effective in reducing the pain of arthritis, and using the therapy in such treatments is the newest trend in PRP.

"Some people are injecting (PRP) into the knee joint in patients that have early osteoarthritis, and they can feel better," Nelson said. "It does not grow new cartilage. It does not reverse the course of cartilage damage. It just helps with the pain associated with arthritis."

For a case like Roy's, more experimental stem cell treatments might hold a better chance in actual healing. It's unclear whether Roy has undergone any such stem cell treatments, but he has received PRP therapy in both his hamstring and his knees. In recent years, some of the biggest names in sports have been associated with the therapy, most notably Kobe Bryant. Bryant, who received the treatment in Germany during the summer of 2011, had been suffering from lingering problems with an arthritic joint in his right knee.

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