I saw a science program on TV about the knee. It showed the ligaments of the knee as strong bands of tissue that work together. If this is true, why do so many people tear the ACL?
The anterior cruciate ligament (ACL) in the knee is made up of many fibers together inside tiny bundles. These bundles aren’t separate from each other, but they do have different jobs. Each bundle is called upon to exert its force during knee motion. Other structures in the knee also work together with the ACL to move and protect the joint. For example, the medial collateral ligament on the inside of the knee joint keeps the knee from moving too far in a sideways direction. The fibrous tissue of the joint capsule helps hold the joint together. Muscles around the knee reinforce the capsular tissue. This is another way the body protects and helps the ACL do its job. The ACL can fail depending on the force placed upon it and the position of the knee. Even though the ACL has some “give” to it, too much force in the wrong direction against it can cause damage and injury. For example, during downhill skiing, if a skier loses control of his or her balance, the skier's weight shifts backward. The ski edge gets fixed in the snow as the skier continues to move forward. There is increased force across the knee. If the ski doesn't come lose and the bindings hold without releasing, the force can cause a ligament to tear or a bone to break. Even the best biology has its limits.