Knee Repair

Knees are the bane of all athletes, but they're particularly nettlesome to aging amateurs, whose joints have endured years of pounding. Fortunately, some of the technology inspired by doctors who treat professional athletes is trickling down to weekend warriors. Scientists are working on a number of strategies to coax the body's healing powers to hasten the repair of damaged knee cartilage.

The knee is particularly tricky because it gets such little blood from the circulatory system, so it's slow to heal. A technique called microfracture surgery is designed to draw blood to the injury. It involves making tiny holes in the bone on either side of the knee socket so that blood from inside the bone can seep up and nourish torn cartilage, supplying it with stem cells needed for repair. Doctors have been refining the technique for the past decade or so, and it's now achieving mainstream use. The problem is that it's difficult to control exactly where cartilage is replaced. With a new technique, called chondrocyte-transplant therapy, doctors avoid this problem by removing cartilage cells from the knee, growing them in a culture and transplanting the new tissue directly in the knee. This procedure, though, calls for opening up the knee twice, which is costly and makes for a long recovery.

Several new techniques obviate the need for extensive surgery. Synthetic growth factors can stimulate adult stem cells in the injured area into replacing damaged tissue. Scientists have used arthroscopes--fiber-optic scopes that require only tiny incisions--to deposit the growth factor in the joints of animals. The least-invasive procedure may be to use viruses to carry growth factor to the injured tissue. Although such techniques will take years to reach widespread use, they may eventually keep our knees functioning well into old age.