The ACL is the most frequently injured part of the knee when related to sports. As fore-mentioned, the ACL aids us in abrupt stops; it are these abrupt stops that are the most common cause for its injury. ( Figure 1. shows the difference between a normal ACL and a torn one.).
An ACL injury has not been scientifically proven to be linked to weight, size, or strength (Duff 308). The cause can be a violent twist of the knee, or it can simply be caused by standing up too fast. It can be twisted or hyper extended. In any case, if it is concluded that the ACL has been ruptured, the symptoms and treatment remain the same. In any injury tiny, or large, blood vessels are broken, resulting in bleeding into the area of the injury. This is the cause of swelling. In an ACL tear, the knee swells almost immediately because of the broken blood vessels in the ligament ( Sechrest.com). The initial tear makes a loud "pop" and, because of the absence of the ligament's reinforcement, there is a feeling of instability in the knee. In some cases, the knee actually subluxes, which is a dislocation that pops back into place on its own. In these cases, there is usually more injured than just the ACL. Often the MCL (medial collateral ligament) is also injured (Sechrest.com). Other common symptoms, according to the northstar website are pain and the athlete falling to the ground as a result of the instability, or buckling, of the knee. .
A torn ACL can only truly be determined through a series of tests starting with a physical examination, as in the Lachman's and Anterior Drawer tests. In the Lachman's test (shown in Fig. 2.), "[the] Patient with suspected injury lies supine on examination table and flexes the knee at 15 degrees. The person examining the patient stands on the affected side of the extremity and holds the patient's femur (thigh) immobile with one hand. The other hand is placed on the tibia (shin) and tries to move it forward, without rotation.
