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This article is from the In-Depth Report The Science of Basketball
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Saving Troubled Knees

Silk scaffolds, grafts from pigs and green tea extracts might someday help keep injured and vulnerable joints active

Green Tea on the Knee

Athletes like Altman who have torn an ACL are perhaps 10 times more likely to develop osteoarthritis than folks in the general population, according to Lohmander. But theyre not the only ones at risk. Arthritis tends to run in families, so genes play a role. So does obesity and even aging itself. Currently no treatments cure the disease. We have drugs, like painkillers and anti-inflammatory agents, that alleviate the symptoms, Lohmander says. But there's nothing that really stops or slows down the development of osteoarthritis once it starts.

Of course, alleviating pain is nothing to scoff at. For some patients, a course of injections of hyaluronate--a molecule normally found in the synovial fluid that keeps the knee joint lubricated--can offer dramatic pain relief. Although the best results are seen with people who have mild to moderate arthritis, even those with severe arthritis may find the treatment worth a shot. Ive had patients who were told that nothing more could be done for them save for a total knee replacement, Chen says. But they come to me every six months for a series of three injections, and they love it. It makes their knee feel great, and they can go out and do the things they want to do.

Unfortunately, as the disease progresses, the damage mounts, and many people with osteoarthritis wind up having a knee replacement. The substitution relieves pain and restores mobility, making it one of the most successful operations in medical history, says Joseph Buckwalter, an orthopedic surgeon and researcher at the University of Iowa Hospitals and Clinics. But the approach has its drawbacks, including the fact that the implants can wear out with time, just as the tires on your car wear out when you drive or your shoes when you walk, Lohmander says.

While prostheses continue to improve--current devices last 20 years or more, and orthopedics manufacturer Zimmer in Warsaw, Ind., recently introduced an artificial knee designed specifically for women--researchers keep searching for more biologically friendly ways to rejuvenate an arthritic joint. Buckwalter and his colleagues have found that as people age, the cells that maintain the knee's articular cartilage begin to fail. The cartilage then weakens, which makes the knee more vulnerable to injury and mechanical malfunction. Treating isolated strips of cartilage in the lab with antioxidants--including purified extracts of green tea--appears to revive those exhausted cells and to prevent or minimize mechanical damage to the joint, Buckwalter says.

Beyond Potholes

Although a whole knee can be replaced, damaged cartilage alone cant be fixed by swapping in something synthetic. The knee goes through two to three million steps per year from normal walking and experiences up to five times the body weight, depending on the height of the step, Stone says. There's no artificial material known to man that you can put in the joint that wont either damage the opposing side or wear down rapidly.

Hence, surgeons have devised a variety of techniques that use some of the patient's own tissue to repair small areas of cartilage damage--nicks, tears or holes that arise from a blow to the knee or some other localized injury. The most common approach involves harvesting a piece of the patient's cartilage and sending it off to a commercial laboratory that multiplies the cartilage cells in a culture dish and ships that expanded material back to the surgeon, who then uses it to patch the knee damage--sort of like filling a pothole, says Farshid Guilak, a bioengineer at Duke University Medical Center.

Guilak is replacing more extensive regions of damaged cartilage by developing stem cells, which have the ability to produce new cells of other types of tissue. The stem cells he uses are a versatile variety harvested from liposuctioned fat. He and his colleagues spread these stem cells over a specially designed woven polyester scaffold. They then bathe this cell-studded material with growth factors that coax the cells to produce cartilage. So far it looks like the cells are up to the job; Guilak and his lab are gearing up to test the scaffold in the hip joints of goats.

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