Beyond the numbers of knee injuries, there's the cost factor, Dr. Hewett said. The ACL controls the pivoting motion of the knee. Simple anatomy is probably a strong factor in women's knee problems, Dr. Hewett said. If the quadriceps and hamstring aren't nearly equal in strength, there's too much strain on the ACL, which can cause it to rupture. Women's hamstrings are significantly weaker than their quads, and women tend to rely more on their quads when they jump and pivot, Dr. Hewett said.
Men rely more on their hamstrings.
The unequal strength between women's hamstrings and quads means the ACL has to work harder to stabilize the knee when women jump. Sometimes the jump puts too much stress on the ligament, causing it to rupture or stretch too much. And the way women jump also plays a part. We don't know why this occurs. We think that's probably not genetic.