Shannan’s Journey

Know About Anterior Cruciate Ligament Tears:

What is the ACL and how big is it?

The anterior cruciate ligament (ACL) is one of four important ligaments of the knee joint. Together, they connect and stabilize the femur (thigh bone) and tibia (shin bone). The ACL crosses the posterior cruciate ligament (PCL) in the center of the knee, which is why they are called cruciate ("forming a cross") ligaments. The other two ligaments are the medial collateral ligament (MCL) and the lateral collateral ligament (LCL) on the sides of the joint. The ACL limits rotation and prevents excessive forward movement of the tibia in relation to the femur. That is why an ACL tear causes instability or feelings of "giving out" of the knee. For such an important ligament, it is surprisingly small. The average length is between 32 and 38 mm. It has an average width of 7 to 12 mm and an average cross-sectional area of 40 mm2, which means that it is only about 1/3 to 1/2 as wide as your pinky finger.

How common is an ACL tear?

There are approximately 200,000 ACL injuries per year, with around 95,000 ruptures.

Why does the ACL tear?

The ACL can tear with contact or non-contact injuries. ACL tears are common in football, basketball, skiing and soccer. Contact injuries occur with a forcible blow to the front of the knee or with somebody falling onto the side of the knee. Non-contact injuries usually involve deceleration or a quick change in direction, when the foot is planted and the body twists in another direction. Also, if the knee is hyperextended more than 10 degrees beyond its fully straight position, the lower leg is forced excessively forward, which can cause a tear.

Are there other injuries associated with an ACL tear?

Over half the time, there are other meniscal or cartilage injuries with ACL tears. The rate is higher the more times there are "giving out" episodes of the knee. Depending on the severity of the injury, other ligaments in the knee can be injured as well. Acute ACL tears will usually show a classic pattern of bone bruising on MRI as the tibia spins forward on the femur.

How do you know if you’ve torn your ACL?

You may hear or feel a "pop" at the time of injury, but not always. The knee usually swells up with blood quite rapidly. Sometimes, however, if the injury is severe enough, the joint capsule may tear and the blood may leak out the back of the knee instead, so you may have bruising in the back of the knee and rather minimal swelling of the joint. If you have a "pop" with immediate swelling, then chances are high that you’ve torn your ACL! You should stop playing, ice the knee and use crutches if you can’t put weight on it. Seek out medical attention. A doctor can examine your knee to tell if it is "loose." Xrays may be taken to make sure you don’t have a fracture. An MRI is beneficial in confirming the ACL tear and seeing if there are any other meniscus or cartilage injuries.

This entry was posted on Tuesday, May 26th, 2009 at 6:58 pm and is filed under Training. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.