Anterior Cruciate Ligament Tear
The anterior cruciate ligament, or ACL, is located in the center of the knee along with the posterior cruciate ligament, or PCL. These ligaments wrap tightly around the femur and the tibia of the leg to form a crisscross pattern in the knee, which prevents the joint from moving too far forward or backward.
Injuries to the ACL are usually sports related. However a torn, stretched, or ruptured ACL can also be caused by repetitive physical stress, such as excessive pivoting or twisting of the knee. ACL injuries generally cause swelling, stiffness, and pain. Many times, a noticeable "popping" noise can be heard at the time the injury occurs.