The latest curative leap to heal professional athletes and weekend warriors alike may sound like science fiction, but it could transform sports medicine. Some doctors and researchers say that in a few years the use of primitive stem cells from infants’ umbilical cord blood could grow new knee ligaments or elbow tendons creating a therapy that becomes the vanguard of sports injury repair.

Already, some sports agents are preparing to advise clients about banking stem cells from their offspring or from tissue taken from their own bodies as an insurance policy against a career-ending infirmity. Stem cell blood banks are promoting the benefits of stem cell therapies for the practical healing and rehabilitation of tendons, ligaments, muscle and cartilage. There are skeptics in the medical community who wonder how soon the technology will be viable, but enthusiastic advocates of the therapies say the time is near.

“It’s not a pie in the sky notion,” said Dr. Scott Rodeo, an orthopedist and award-winning research scientist at Manhattan’s Hospital for Special Surgery. “Maybe it’s not going to happen next year, but a three-to-five-year horizon is not unreasonable.”

Dr. Rodeo has already practiced these technologies in laboratory surgeries on rats, methods that will be especially useful when reconstructing the knee’s anterior cruciate ligament and the shoulder’s rotator cuff. Both are common sports maladies that can be particularly daunting to surgeons because the body generally does not mend or restore the damaged tissue after these injuries.