Article Series--Lower Leg Injuries and Exercise, Part 3
Posted Aug 24 2008 7:30pm
A knee anterior cruciate ligament (ACL) injury is the most common injury affecting the knee joint. About 70% of all serious knee injuries involve damage to the ACL. And, about 80% of these injuries occur without any contact (i.e., jumping, landing , etc.). There are some training techniques you can use to lessen the risk of this injury. The knee ACL is located within the capsule of the knee and connects the thigh bone (femur) to the shin bone (tibia). Pictured below is a torn knee ACL:
Most ACL injuries occur when you decelerate, come to a sudden stop or land with improper technique while placing too much stress on the knees. You should dominate the hamstrings, hips and glutes during movement. The hips are often under-used when running. Another common mechanical breakdown is when the knees protrude far in front of the feet when decelerating, landing or squatting. This puts undue stress on the knees and often causes injury. Also, when the quadriceps are much stronger than the hamstrings, this can cause an ACL injury. Research has shown that the hamstrings play an important role in stabilizing the knee and protecting the ACL during deceleration.
Females injure their ACLs at six times the rate of males. Females demonstrate a lower hamstring to quadricep ratio. This means they typically have weaker hamstrings compared to males. They also demonstrate different muscle activation patterns compared to males. Females are typically quadricep dominant which means they use their strong quadriceps muscles and do not use their weak hamstrings enough. Strength training for females should be adjusted to adequately strengthen the hamstrings.
Surgery will be necessary for a tear of the ACL. Usually, the tear is repaired by using a part of another healthy ligament to replace the damaged ACL. Rehabiliation for a torn ACL takes about 3-4 months and it takes 8 months or more before you can return to normal exercise activities.