ACL – WHAT IS IT? WHY IS AN ACL INJURY SO DEVASTATING?

What is the ACL? 

ACL stands for the anterior cruciate ligament, a ligament in the central aspect of the knee responsible for ACL Injuries controlling anterior translation and rotation. The functioning ACL is critical in performing the cutting and pivoting activities associated with sports like soccer, football, volleyball, & basketball. Injury to the ACL can occur in a contact or non-contact fashion – female athletes sustain non-contact injuries predominantly while planting a foot to change directions or landing awkwardly from a jump, where as their male counterparts have a relatively higher incidence of contact injuries due to collision sports like football, rugby, hockey, & lacrosse.

Female athletes unfortunately sustain ACL injuries at a rate 4-8x that of male athletes; this is due to a variety of reasons. Differences in anatomy result in a relatively smaller ligament and a narrower intercondylar notch of the knee, which houses the ligament, leading to a propensity to tear the ACL with a hyperextension or torsional episode. Similarly women have a wider pelvis and hips, which creates higher valgus forces at the knee, contributing to ACL injuries. Various hormonal receptors (i.e. estrogen) on the ACL may alter its susceptibility to injury during various stages of the female athlete’s menstrual cycle. Differences in neuromuscular firing patterns, specifically the sequence in which male & female athletes engage their hamstring & quadriceps muscles with cutting or landing activities, also are believed to contribute to the heightened ACL injury risk in female athletes.

ACL injuries can be devastating, occurring abruptly, and generally are season-ending. Patients often describe feeling a pop and a giving way or shifting sensation in their knee. Hyperextension injuries are a common mechanism. The athlete may present in a variety of ways – generally the individual is unable to weight-bear fully and thus is unable to continue participation, although in rare instances the athlete can “walk it off” and return to play, unknowingly putting the individual at risk for further injury. ACL tears typically are associated with the rapid onset of swelling in the affected knee. A typical office evaluation includes:

• A detailed history
• Comprehensive physical exam
• X-rays
  
  

X-rays are obtained to rule out any bony injuries, assess the growth plates in the adolescent athlete, and evaluate the older athlete for early arthritic changes. An MRI is normally obtained to confirm the diagnosis suspected from the history and physical exam. Sometimes the knee is drained of blood if there is sufficient swelling. The patient is provided with crutches to assist in weight-bearing and help rest the knee, aiding in reducing swelling and improving range of motion. A brace is utilized in the event the knee feels too unstable to partially weight-bear with the crutches. Icing, elevation, compression, and anti-inflammatories are recommended as well to combat pain and swelling. The athlete is instructed on a home exercise program to regain full knee extension and flexion while also assisting in quadriceps muscle tone recovery. In most cases, surgery is needed to repair the torn ligament.