Injury to the anterior cruciate ligament (ACL) of the knee can be devastating for both competitive and recreational athletes. An estimated 80,000 to 250,000 ACL injuries occur each year. The cost is high both in financial terms (an estimated cost of $20,000 - $30,000 per repair procedure), and personal terms (an average recovery time after ACL surgery is 9-12 months).
There are preventive measures that athletes can take to avoid an ACL injury. Conditioning programs that improve strength and flexibility of the hamstring and quadriceps muscle groups can help protect the ACL. Improving overall conditioning will also help prevent injury, as ACL injuries occur more often in the late part of games, when the athlete is fatigued. Finally, ACL care programs should include exercises that improve the athlete's balance, which has been shown to decrease injury rates.
Mechanism of Injury in ACL Tears
The majority of ACL tears occur in a non-contact setting. Injury usually occur from either a jump, a rapid deceleration from running, or a quick change in direction (cutting). The knee is usually fully extended at the time of injury, and excessive force is loaded on the ligament while it is taut (and vulnerable to tearing).
Preventive Measures Against ACL Tear
- Strengthening the Hamstring and Quadriceps Muscle Groups – The hamstring muscles, located on the back of the thigh, and the quadriceps muscles, on the front of the thigh, act to stabilize the knee joint. Strengthening these muscles has a protective effect on the knee, and can decrease the stress on the knee joint during play. A strong hamstring group, in particular, can have a protective effect by preventing hyperextension of the knee joint (the position most conducive to ACL tear).
- Improving Overall Endurance/Fitness – Several studies have shown that knee injuries are more common at the end of games, when athletes are fatigued. These studies suggest that fatigue leads to poor muscular control, increased incidence of knee hyperextension, and increased vulnerability to ACL tear. Increased endurance through improved overall fitness can help mitigate this risk.
- Improving Overall Balance – Poor balance can lead to increased extension of the knee after jumping or when changing direction on the run. Balance techniques, including so-called plyometric exercise, will decrease the incidence of full knee extension, and decrease the risk of ACL tear.
Other Risk Factors
Other factors that increase the risk of ACL injury include use of high traction or cleated footwear, and high friction, hard playing surfaces. The increased traction from a “fast” playing surface and specialized footwear translates to increased shearing force on the knee, resulting in a higher ACL injury rate. Use of lower friction footwear and softer playing surfaces can decrease the risk of ACL tear.
For more information, see sportsinjurybulletin.com
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