In an effort to revive his NBA career, Greg Oden recently underwent the controversial knee procedure that superstars Kobe Bryant and New York Yankees slugger Alex Rodriguez say helped prolong their careers, according to sources.

Oden, whose career with the Portland Trail Blazers was derailed by four knee surgeries, had the noninvasive procedure done in New York two weeks ago to accelerate the healing process on his left knee, which was operated on in February.

"Greg had long planned to have this procedure done,'' one of the sources said. "He thought he'd wait until his knee was completely healed, but the doctor said Greg would get the greatest benefit by doing it now because it would help his recovery.''

Bryant underwent the procedure, known as Orthokine, in Germany last offseason to relieve pain in his right knee and left ankle and returned to have a historically productive year in this, his 16th NBA season. Under Bryant's advice, Yankees superstar Rodriguez flew to Dusseldorf to have the procedure done in December. Gilbert Arenas also had the procedure done.

The procedure involves doctors taking the patient's own blood, spinning it in a centrifuge, making a serum and then injecting it into the knee. Doctors claim the blood then works to stop inflammation and reduce pain and cartilage damage.

The 7-foot Oden is not considering retirement, and while it's possible he could play by the middle of next season, there is no timetable for his return. Oden, the top pick of the 2007 draft, is an unrestricted free agent and about seven NBA teams stay in contact with his representatives to monitor his progress, according to the sources.

Oden has had two microfracture surgeries on his left knee and another on his right, as well as surgery to repair his broken left kneecap. He appeared in just 82 games during his five-year career with the Blazers and has not played since Dec. 5, 2009. He averaged 9.4 points and 7.3 rebounds.

Oden is currently rehabbing at the sports performance division of St. Vincent's Hospital in Indianapolis. He recently enrolled for summer school at Ohio State, where he played for one season before turning pro.