Knee injury surfacing in kids

Last year, when Collin Link was 11, he was tackled as he went in for a touchdown in pee-wee football.

"He didn't get up," his mother, Crystal Link, said. "He kept saying his knee hurt real bad." But she was not overly concerned, thinking it was just a sprain.

But the next morning, The Woodlands, Texas, boy said he could not walk. That Monday, a doctor told the Links why.

Collin had an injury that doctors used to think hardly ever occurred in children: He had torn the anterior cruciate ligament, or ACL, in his left knee, the main ligament that stabilizes the joint.

The standard treatment in adults is surgery. But the operation poses a greater risk for still-growing children and teens because it involves drilling into a growth plate, an area of still-developing tissue at the end of the leg bone.

Although there are no complete or official numbers, orthopedists at leading medical centers estimate that several thousand children and young adolescents are getting ACL tears each year, with the number being diagnosed soaring recently.

And contrary to the old belief that boys are more prone to the injury than girls, as many as eight times more girls than boys are suffering the tears, doctors report.

It is not an overuse injury from playing one sport too intensively, like shoulder injuries in young pitchers. Instead, doctors say, the injury occurs simply from twisting the knee, and diagnoses are on the rise partly because it now can be easily detected and partly because the very nature of youth sports has changed.

In the old days, said Theodore Ganley, director of sports medicine at the Children's Hospital of Philadelphia and a spokesman for the American Academy of Orthopedic Medicine, a child would develop a "trick knee" that made sports difficult, but the real reason was not understood. And most doctors, thinking children did not get ACL tears, did not suspect the real reason.

Now that almost every child with a hurt knee gets a magnetic resonance imaging (MRI), doctors are finding the ligament tears on a regular basis.

The other reason for the reported surge, doctors speculate, is that the best athletes are constantly at risk, playing year-round and on multiple teams with frequent games.

"The kids are playing at really highly competitive levels at earlier and earlier ages," said Mininder Kocher, the associate director of the division of sports medicine at Children's Hospital in Boston.

Familiar injury

Every orthopedist is familiar with ACL tears — in adults. It is "the most common and most dreaded injury in professional sports," Kocher said. The operation to repair it often results in a full return to function. And doctors often recommend that adults have the operation because without the ligament the knee is not stable.

After a tear, any sport, like soccer or basketball, that can twist the knee is dangerous. Without an ACL, even everyday activities can injure the smooth, shock-absorbing cartilage that caps the knee joint. "Then you are on your way to arthritis," Kocher said.

But the standard ACL repair operation, which entails drilling into the growth plate, may cause permanent damage to the still-growing bones of young children. After drilling, surgeons replace the torn ligament with a tendon taken from elsewhere in the body, like the hamstring, or from a cadaver. But if the drilling damages a growth plate, the leg bone will not develop normally.

That happened recently to a 14-year-old boy who was referred to Freddie Fu, an orthopedic surgeon at the University of Pittsburgh. A year after the operation, Fu said, the leg with the repair was bowed 20 degrees on one side and was shorter than the other leg.

"I had to go in on the other side and stop the growth," Fu said. "Now, about six months later, the leg is still crooked. There still is a 2-inch difference in length which I have to fix." The boy, he said, "will be a little bit shorter" as a result, although both legs will be the same length.

Doctors often suggest putting a brace on the injured knee and limiting activities, delaying surgery until the child finishes growing. But the children tend to be competitive athletes who chafe under the restrictions.

New methods

Some surgeons are developing new and technically demanding methods to repair ACL tears in children, drilling holes to create little tunnels in bone that is already finished growing and threading tendons around the growth plate. Different surgeons have different versions of the technique, Ganley said.

But the tendons are not anchored where they would normally be and the long-term effects are not known.

Kocher has perhaps the most extensive data, on 59 young patients. His results are encouraging; the implanted ligaments failed in only two patients and no patients had severe growth abnormalities. But the patients have been followed less than four years.

It is only with the new increase in diagnosed ACL tears in children, orthopedists say, that they discovered how mistaken they once were about this injury.

Doctors used to think the tears did not occur or were rare in children because children's ligaments were stronger than their bones. They thought an injury that would rip an adult's would, in children, result in a broken bone.

Another myth, Ganley said, is that ACL tears arise mostly in contact injuries, like a tackle in football, and almost exclusively affect boys. Now, though, it appears that girls are more susceptible, although no one really knows why, Willis said.

Doctors also have learned that contact injuries are not the most common cause of ACL injuries. It turns out, Ganley said, that tears occur more often from twisting and jumping. A child can be running and step in a hole, twisting a leg. Or they can fall off a bike, like Malinda McCartney of Pembroke, Mass., who tore her ligament last year when she was 9.

Other times, a young athlete can tear an ACL by coming down from a rebound in basketball or by accelerating and decelerating.