But for young athletes, that same running, jumping and kicking during a sports competition can bring physical pain and injury to their growing bodies, and especially the knees. And now, it appears that the injuries may come back to haunt them in the future.

With more children and adolescents taking part in sports activities, it's even more important for them to learn how to properly condition and warm-up to prevent injuries and decrease the risk of long-term knee problems, says Edward Wojtys, M.D., professor, Department of Orthopaedic Surgery, and director of Sports Medicine at the University of Michigan Health System.

"Knee injuries with adolescents are actually quite common," he says. "We see people every week in our clinics in the same situation -- a young athlete who was injured at age 12 or 16 and now, at the ripe old age of 25 or 30, he's experiencing debilitating knee pain or constant swelling."

With sports that involve a lot of running, jumping, kicking, turning and twisting, there's always the risk of a knee becoming injured. Sports like basketball, gymnastics, volleyball and football tend to produce the most severe knee injuries.

Many knee injuries in young athletes are minor -- just bruises and strains that quickly heal. But injuries involving ligaments, cartilage or bone fractures may lead to serious consequences.

At a time when an adolescent's bones are growing, fractures near the body's growth plates, the area of developing tissues at the end of the long bones, can seriously alter growth.

Typically, growth plates are open in young females before age 12 or 13 and in young males before age 14 or 15. A bone fracture during this time can cause the plate to stop growing or to grow in an abnormal fashion, says Wojtys.

Just as harmful to growing bodies are injuries to ligaments, the elastic bands of tissue that connect the bones at the joints. When ligaments are stretched too far or torn, a joint can become unstable. This may cause irreversible damage to the knee's internal structures like the menisci, the pads of connective tissue that absorb shock and cushion the lower part of the leg from the weight of the body.

Despite an orthopedic surgeon's best efforts, damage to the knee's menisci or articular cartilage, a tough, elastic material that helps absorb shock and allows the knee joint to move smoothly, often cannot be repaired.

And once the damage is done, an athlete may start down the road to degenerative arthritis, a disease in which cartilage in the joint gradually wears away. Arthritis of the knee can cause pain, swelling and a decrease in knee motion.

But how quickly arthritis develops after a serious knee injury often depends upon the lifestyle, body weight and physical conditioning of the individual. If an athlete continues to play high-impact sports and the ligaments or cartilage are further damaged, the results can be devastating.

The best way to prevent future pain and debilitation is to minimize the risk of knee injuries. Wojtys recommends that young athletes take part in a conditioning program throughout the entire year, not just before a particular sport's season. Conditioning can help develop the strength and agility necessary to protect joints from injury.

To further prevent knee injury, the National Institute of Arthritis and Musculoskeletal and Skin Disease suggests that parents make sure their child wears proper protective sports gear, in addition to stretching and lightly jogging to warm-up their muscles before a game.

Yet there's always a chance for injury, even if the body is properly protected and conditioned. And when an injury occurs during a game, an athlete needs to decide if he or she will continue to play or seek medical assistance.

In most adolescents, Wojtys says "playing through the pain" shouldn't even be an option when an athlete injures his knee during a game.

"Pain is one of the ways the body tells you that something is wrong," says Wojtys. "Very few individuals realize that swelling and pain caused by an injury diminishes the muscle's capacity to protect the knees, causing an athlete to be even more vulnerable to serious injury."

Bryon Tansel, a varsity football player for the Dundee High School Vikings, knows all-too-well the gravity and pain of injuring a knee mid-game.

The 16-year-old injured his knee during a defensive play with one of his teammates. When the pair hit the opposing team's quarterback, Tansel's knee was twisted beneath his body and snapped. As a result, he needed surgery to repair damage to his anterior cruciate ligament and meniscus.

Now, after his surgery, Tansel has about six months of physical therapy rehabilitation ahead of him to allow his ligament and meniscus to heal.

"I've already gone through a couple of injuries and I know it's a lot of hard work," says Tansel. "But we 're going to do whatever it takes to get back to 100 percent." - By Krista Hopson

Facts about adolescent knee injuries:

Sports such as basketball, gymnastics, volleyball and football that involve a lot of running, jumping, kicking, turning and twisting can lead to the most severe knee injuries.

Fractures around the body's growth plates, especially near joints, can seriously damage the plate's growth or cause it to grow in an abnormal fashion.

Ligament and cartilage injuries and bone fractures during adolescence may lead to arthritis.

How quickly arthritis develops after a knee injury depends on an individual's lifestyle and whether or not he or she continues to play sports.

To prevent knee injuries, all athletes should properly condition their bodies throughout the year, stretch and lightly jog before a game to warm-up muscles, and wear proper protective sports gear.

Related websites:

U-M Health Topics A - Z: Knee Problems

U-M Health Topics A - Z: Arthritis of the Knee

U-M Health Topics A - Z: Tendinitis/Ruptured Tendons

U-M Health Topics A - Z: Orthopaedic Surgery

National Institute of Arthritis and Musculoskeletal and Skin Disease

American Academy of Physical Medicine and Rehabilitation

14-Dec-2001