ACL tear is a common sports injury to the knee. ACL is short for Anterior Cruciate Ligament. There are four main ligaments that hold the knee together. The two side ligaments (the collateral ligaments, MCL and LCL) keep the knee from shifting side to side. The two central ligaments are the cruciate ligaments and keep the knee from shifting forward or backward. Anterior means front and cruciate means crossing, so the anterior cruciate ligament is the front crossing ligament. It is a rope-like structure that runs from the femur (thigh bone) to the tibia (shin bone) at an angle that prevents the tibia from sliding too far forward.
It is injured in sports by a hyperextension or twisting injury. These can be contact or non-contact injuries. Sports that have frequent pivoting or sudden changes in direction are more risky for ACL injury. The patient often falls to the ground and has pain and notable swelling fairly quickly. These symptoms often subside over a few weeks, but if the patient returns to sports the knee may give way easily since the ACL does not provide its normal stability. It does not heal well after being torn. This is why for young active athletic patients it is common to recommend a surgery. Years ago attempts to repair the ligament were not very successful. Now, it is common to remove the damaged ligament and replace (reconstruct) it with a substitute (graft), often the hamstring tendons. Bracing can be an option for some patients if they are not regular participants in risky sports. One concern with ACL tears is the frequent occurrence of other injuries such as meniscus tears or MCL (medial collateral ligament) tear. Then a treatment plan has to be made for the combined injuries.