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Winter 2014 The Ins and Outs of ACLs

ACL (anterior cruciate ligament) injuries are not uncommon in the adolescent athlete

There is debate on whether there has been a true increase in injuries to the ACL or whether increased awareness has led to greater recognition and thus, the reported number of these injuries. Additionally, an increase in the number of high-level female athletes may be associated with an increase in the number of ACL injuries because the female knee is uniquely vulnerable to these injuries.

What is an ACL injury?

There are four major ligaments in the knee; the ACL being one. The ACL resides in the center of the knee (notch). It originates from the lateral femoral condyle and inserts in the center of the tibia on the tibial spine. It is composed of two parts (bundles), which control anterior-posterior motion (anterior bundle) and rotation (posterior bundle) of the knee. Other structures, including but not limited to the muscles and cartilage of the knee, provide stability to the knee as well.

Most injuries to the ACL result from non-contact mechanisms, i.e. changing directions or landing awkwardly from a jump. The injured athlete may hear/feel a "pop" at the time of the injury. Often the injury results in a large knee effusion. Unfortunately, the female knee is uniquely vulnerable to this type of injury. (See 'Soft Landing: ACL Injury Prevention' for more information.) It is rare for an athlete to return to play during the game in which the injury occurred. 

Treatment and Rehabilitation 

Treatment of ACL injuries depends on the goals of the patient, and can range from therapy and bracing alone to reconstruction. A recent study published in the New England Journal of Medicine (Frobell et al, 2010) looked at patients age 18-35 with an ACL tear; half were randomly chosen for rehabilitation and early reconstruction, and half for rehabilitation and optional delayed reconstruction. After two years, they concluded there were no functional differences in patient outcomes and recommended delaying ACL reconstruction in the recreational athlete.

In either situation, proper rehabilitation is essential to regain range of motion, strength, endurance and agility. This stepwise process focuses on restoring dynamic stabilization of the knee through the muscle-tendon units – the normal "braking" system of the knee – so that the "emergency brake" ACL is protected.

Better Prevention Strategies?

There is debate about whether or not ACL prevention programs work. Several randomized trials have been published concluding that the program resulted in decreased ACL tears. However, in a systematic review of 10 well-designed Level 1 trials, Grimm et al (Clinical Orthopaedics and Related Research, Jan 2013) concluded that eight out of 10 studies showed no benefit, especially with regard to female-specific studies. Understanding the root causes of ACL tears, whether it be structural, genetic, neuromuscular or overuse-related, would go a long way to designing effective prevention strategies.

Article is written by Donna M. Pacicca, MD, and Kevin H. Latz, MD.  

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