It seems like ACL tears are one of the more common injuries in the Colorado mountains. How do they occur and how would I know if I tore mine?

You are correct; ACL tears are a common knee ligament injury often occurring as a result of an athletic injury.

Anatomy of the ACL Tear and Mechanism of Injury

The ACL is one of the primary stabilizing ligaments of the knee. It originates from the back of the femur (thigh bone) and inserts on the front of the tibia (shin bone). It is about the size of your small finger but can withstand forces of up to 500 lbs. before it ruptures.

The ACL minimizes excessive forward movement and rotation of the tibia in relationship to the femur. A tear of the anterior cruciate ligament (ACL) results from over stretching of the ligament. It is the most commonly injured ligament in the knee.

How ACL Tears Occur

An injury to the ACL can occur as the result of a slow, twisting fall skiing or with a sudden deceleration in cutting and pivoting sports such as football, basketball or soccer. It is most often a non-contact injury. Women are three to five times more likely than male athletes to tear their ACL for a number of biomechanical reasons.

Complete and Partial ACL Tears

The vast majority of ACL tears are complete tears, but one can occasionally suffer only a partial tear. Most people report feeling their knee give way, hearing a pop in the knee, and then having immediate pain and swelling.

Pain is commonly located on the outside or lateral aspect of the knee. However, patients can also tear the medial collateral ligament (MCL) or medial meniscus, which can cause pain on the medial or inside of the knee.

What Does an ACL Tear Feel Like?

People can typically walk on the knee with pain after such an injury, but they may feel that their knee gives way or feels weak. Oftentimes, other structures, such as the meniscus cartilages, are also injured in the knee when the ACL tears. However, after four to six weeks, the knee can feel nearly normal and one can do non-athletic, everyday activities.