Sports Medicine Miracles?

Designer "spare parts" for ruptured tendons and torn ligaments. Stem cell injections to heal and build muscle. Medical therapeutics that would allow star athletes to extend their careers by years, if not decades.

Welcome to what some envision as the new world of sports therapeutics. Proponents say that such regenerative treatments could be on the way in the years to come.

Clinical trials investigating stem cells' potential in regenerating cartilage and healing muscle are currently under way. And already, some companies that freeze and store certain types of stem cells are promoting the potential of stem cell therapies for sports medicine. The idea is that stem cells stored now may be useful years down the road.

But other stem cell and regenerative medicine experts say today's sports stars shouldn't call their agents yet because much more research needs to be done before such treatments even approach reality.

Better Athletes Through Science?

Research on stem cells -- those cells in the body that can be nudged to develop into a wide variety of different tissues -- has actually been going on since the early 1960s.

However, recent advancements have brought the type of optimism that, some argue, hasn't been seen in scientific realms since the beginning of the atomic age.

The regenerative stem cell therapies that may one day help athletes heal mostly fall outside the debate over research on embryonic stem cells; in most cases, the cells used in sports medicine would come from other sources, such as umbilical cord blood or even the patients themselves.

Initial steps in stem cell therapy for athletes could be modest.

"The most likely short-term applications of stem cells would seem to be the enhancement of the healing response after injury and or surgery," said Dr. Rick Matsen, chair of orthopedics and sports medicine at the University of Washington.

As an example, he said that stem cells may one day be used to help torn rotator cuffs heal more quickly. Stem cells may also be used to prompt quicker healing of stress fractures and muscle strains.

Still, some researchers are optimistic that sports medicine could reap the benefits of stem cells in the foreseeable future.

Dr. Johnny Huard, director of the Stem Cell Research Center of the Children's Hospital of Pittsburgh, said his team has already conducted stem cell research that treats patients using their own muscle stem cells.

In this case, the patients were not athletes -- they were men with bladder problems. But he said the research demonstrates that these procedures are safe.

"When can we apply this to sports medicine? Time will tell us," he said. "But we believe that this is in our sight."

Others say future stem cell treatments could target knee joints and other problematic areas for athletes.

"In athletes, we will probably first see stem cells being used to treat meniscus injuries in the knee and tendon injuries," said Dr. Scott Rodeo, associate attending orthopedic surgeon at the Hospital for Special Surgery and associate team physician for the New York Giants.

"We could also see it used in ligament reconstruction in the knee. ACL repair is a common operation -- typically you take part of a ligament from a donor site in the knee. Instead we might be able to use a patient's own cells to grow their own ligament. That would be cool."

And one company is currently in the early phases of a clinical trial for a new technique to repair the meniscus -- a crucial wedge of cartilage in the knee joint.

"So far it's been very safe," said Randall Mills, CEO of Osiris Therapeutics. Although the trial is still in its early stages, he said these therapies may one day allow athletes to heal more completely and faster than ever before.

"Stem cell therapy is much closer than people think," he said. "Once that happens, it's really going to open up the door for large-scale stem cell therapies to invade into other areas and become part of the armament of sports medicine physicians."

Treatments Still Highly Speculative

But the meniscus project's researcher Dr. Tom Vangsness, professor of orthopedic surgery at the University of Southern California's Keck School of Medicine, said that though initial steps appear promising, researchers are still a long way from practical application of stem cells in sports medicine.

"We have only been playing with [stem cells] for a few years now," he said. "We don't know what they can do yet, in all honesty. The FDA will not in the near foreseeable future allow any human application of stem cells in sports medicine."

Other researchers agree that many hurdles remain before treatments become widely available.

"Even after a tissue has been generated outside the body, one still has the challenge of getting it in place and assuring that it becomes functional," Matsen said. "The bottom line is that there is much research to be done to explore the effectiveness of stem cell technologies in solving the cartilage, ligament, tendon and bone injuries we face in athletes and in all active individuals."

These and other complexities could mean years of research before practical applications are seen.

"In five years, the hope is to be engaged in meaningful clinical trials," Rodeo said. "There are safety issues we still need to work out."

At the earliest, he said, it would take two to three years for legitimate treatments to follow successful clinical trial results.

"We're not at the point where we can make recommendations for stem cell treatment on a routine basis. Eventually, the answer may be yes. The cells have tremendous potential to regenerate things that don't really heal."

Some Athletes May Not Wait

Some athletes may already be taking steps toward stem cell solutions, even though no definitive research exists.

Stem cell banks already offer their services in freezing and storing adult stem cells for the possibility of later therapeutic use.

"Absolutely it is logical," Huard said, adding that stem cell banking for young children who show athletic potential should be considered.

But the potential of stem cells in sports medicine has a worrying side as well. Vangsness said that if promising preliminary results come out of early trials, some athletes may look to reap their benefits before they are approved in the United States -- or even proven safe.

"Professional athletes are privileged," he said. "They have money, and they have access to certain things that the rest of us do not."

Huard said that once the technology matures, there may even be a possibility that some could see stem cells as the next steroids.

"We're not there yet, but I am already thinking that some people would be interested to do that," he said.

Still, the greatest danger that exists for the time being, Vangsness said, is the possibility that stem cell therapy in sports medicine could be oversold -- even before it has become a reality.

"We want to be absolutely responsible in terms of what we are saying to the public," he said. "People are really tuned in to this, and they are desperate in many ways. This is not a panacea, but still, it is clearly the most exciting frontier in medical science that we have ever seen."

ABC News Medical Unit intern Junko Takeshita contributed to this article.