ACL

As discussed in the anatomy section, the anterior cruciate ligament (ACL) keeps the lower leg (tibia) from sliding too far forward (anterior) on the upper leg (femur). If the tibia does move too far anteriorly, the ACL can tear.

The ACL can be torn by excessive twisting, extension (hyperextension), or forward sliding of the tibia over the femur. When torn, it unravels like a braided rope and generally does not heal on its own. Fortunately, reconstruction surgery can help many people recover and have a fully functioning knee after an ACL tear.

The ACL suffers more injuries than any other ligament in the knee and is often accompanied by collateral ligament tears or a torn meniscus.