I am on the girls’ basketball team for my high school. Last week, I worked out at the gym and then played a pick-up game on the court. An hour into play, I landed a jump and tore my ACL. I thought my work-out routine would protect me. What happened? Why didn’t it work?

Fatigue may be a factor — at least according to several studies on the effect of fatigue on the knee. It appears that fatigue leads to a decreased sense of joint position called proprioception. The number of fibers that get activated is reduced with fatigue, too.

When jumping, cutting, pivoting, and shifting weight suddenly through the foot and leg, the knee can get injured. Adding fatigue as a factor increases the risk of injury. With fatigue comes decreased neuromuscular control and a decreased ability to control movements. Landing forces can exceed the muscular control needed to slow the movement and avoid injury.

This is just one of many possible explanations. Limited information on the status of the muscles and their function right before injury make it difficult to find out exactly what went wrong. But scientists are studying large groups of athletes then taking a look back at the data after someone gets hurt. The hope is to identify possible risk factors and reduce as many as possible.