A Patient's Guide to Collateral Ligament Injuries Introduction The collateral ligaments are commonly injured parts of the knee. An injury to these ligaments usually involves a significant force, such as a fall while skiing or a direct impact to the side of the leg. This guide will help you understand where the collateral ligaments are located how a collateral ligament injury causes problems how doctors treat the condition Anatomy Where are the collateral ligaments, and what do they do? Ligaments are tough bands of tissue that connect the ends of bones together. There are two collateral ligaments, one on either side of the knee, that limit side to side motion of the knee. The medial collateral ligament (MCL) is found on the side of the knee closest to the other knee. The lateral collateral ligament (LCL) is found on the opposite side of the knee. Together, the collateral ligaments also work with the posterior cruciate ligament (PCL) to prevent excessi