The anterior cruciate ligament (ACL) is one of the most frequently injured ligaments in the knee. Each year 100,000-200,000 ACL injuries are reported in the United States. The primary function of the ACL is to prevent forward movement of the tibia on the femur and to assist with stabilizing the knee during high velocity movements. When the ACL is torn, individuals often feel instability, as if the knee is “giving out.”
Am I at Risk?
The most common way of injuring the ACL is through non-contact movements such as pivoting and jumping. Risk factors for experiencing an ACL injury can be separated into two groups: non-modifiable and modifiable. Non-modifiable risk factors including gender, family history, bony structure and laxity of the ligament cannot be altered with exercise. However, modifiable risk factors such as landing and jumping mechanics, poor body awareness and hamstring, core and gluteal muscle weakness can be improved with detailed guidance. The most common cause of an ACL tear is through a combination of movements that incorporate inward motion of the knee and inward rotation at the hip.
ACL Prevention Program
Although an ACL tear cannot be completely prevented, implementing an ACL prevention program may decrease the risk of injuring this ligament. An ACL prevention program can be separated into four phases: mobility, strengthening, landing mechanics, and body awareness.
The first phase should focus on assessing range of motion of the ankles, knees, hips, and trunk. If the individual does not display adequate motion in these joints, he or she may be at risk for placing increased stress on the knee. Therefore, gaining motion in these joints should be the main priority before progressing through the ACL prevention program.
The second phase involves strengthening the posterior chain, which includes the hamstrings, gluteus medius, and gluteus maximum. These muscles control the movements that prevent inward motion and rotation of the knee during landing, pivoting, and jumping activities. Exercises that target these muscles include squats, deadlifts, bridging, poor man’s glute-ham raises and hamstring curls on a swissball.
The third phase of the program focuses on correct landing mechanics and should be addressed only when the individual demonstrates sufficient lower body strength. When jumping, the individual should land with knees bent in order to absorb the impact. The knees should also be aligned with the toes, preventing inward motion of the knees.
The final phase emphasizes proper body awareness when performing high-level activities. The individual should be taught to land equally on each leg in order to avoid placing greater stress on one knee. Therefore, training should involve side-to-side drills that incorporate single leg balancing and strengthening exercises. This phase should also contain strengthening exercises that target the abdominals, back extensors and oblique muscles because these muscles stabilize the trunk and allow for a more symmetrical landing position. The EDGE facility at Southwest Health does an excellent job of incorporating these phases into their sports performance training and ACL Bridge program.
What to Remember
ACL tears cannot be completely prevented, but incorporating an ACL prevention program into your regular training program can reduce the risks. If an injury does occur, a physician, physical therapist, or orthopedic specialist should be contacted to address any concerns. For further questions or additional information, please contact the The EDGE (608.342.4790) or The Orthopedic Institute and Physical Therapy Rehab Department (608.342.4748).
Joshua Bruner, PT, DPT, CSCS
Certified Strength and Conditioning Specialist
Direct: (608) 342 – 5081