ACL injuries are ten times more frequent in females than males. The reason for this isn’t completely clear, though evidence points to differences in anatomy, knee alignment, ligament flexibility, and muscle strength.
In the knee, an intercondylar notch (or compartment) sits in the middle of the two rounded ends of the femur (thigh bone). The ACL moves inside this notch, connecting the femur and shin bone, which gives the knee stability. Females have a smaller notch than males. Consequently, the area for ACL movement is more limited, making it easier for the ACL to get pinched by the femur as the knee straightens and bends, particularly while twisting or doing hyperextension movement.
Alignment of the Knee
The femur meets the tibia at the quadriceps (or Q) angle. The width of the pelvis is the determining factor in the size of the Q angle. A female pelvis is wider than a male pelvis; in turn, a woman’s Q angle is bigger in women than men. Because of this, more force is transferred to a woman’s ligament when the knee twists, increasing the possibility of an ACL tear.
Female hormones create increased flexibility and muscle, ligament and tendon looseness. This aids in preventing a number of injuries, but not necessarily an ACL injury. If the ligaments and muscles around the knee are too loose, they won’t be able to absorb the stress placed on them and the impact will be put directly on the ACL, causing a higher likelihood of rupturing.
Women and men participating in the same sporting events have almost equal forces placed on the knee joints. The muscles that hold the knee in place are stronger in males than females, and women have less muscle strength in proportion to bone size. Women’s ACLs often have extra strain placed on them, because of the smaller amount of muscle strength; this is another factor that increases the chance of a rupture.
There’s no one exercise for ACL injury prevention. Women and men can reduce the risk of a knee injury by building and maintaining strength and endurance in the lower body. Knee stability can be increased by participating in exercises such as leg presses, squats, lunges, etc. Diversification in cardiovascular workouts can also be helpful, such as rotating among the stair climber, stationary bike, elliptical cross-trainer, and the ski machine.
If you play sports, it’s a good measure of prevention to begin endurance training at least four weeks ahead of the season’s start.