By Ginal Kolata

February 18th, 2008

The New York Times

Last year, when Collin Link was 11 years old, 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 Mrs. Link was not overly concerned, thinking it was just a sprain.

But the next morning when the family was getting ready to go to church near their home in The Woodlands, Tex., Collin said he could not walk. That Monday, a doctor told the Links what was wrong.

Collin had an injury that doctors used to think almost never occurred in children. He had torn the anterior cruciate ligament, or A.C.L., in his left knee, the main ligament that stabilizes the joint.

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