Introduction
As discussed the knee by design of the interacting surfaces starts with a very unstable mechanical situation. The function of ligaments is to attach bones to bones and provide strength and stability. Ligaments are strong, tough bands which are not necessarily flexible and therefore once they are stretched they weaken and if the stretching is excessive they can rupture.
The two most important ligaments for stability are the anterior and posterior cruciate ligaments which are situated deep and centrally within the knee joint in criss cross fashion. They enable the tibia to flex and extend back and forth under the femur but prevent the tibia sliding too far anterior or posterior.
The anterior cruciate ligament extends from a slightly lateral location posteriorly, and insert slightly medially, anterior to the posterior cruciate. It prevents excessive rotation and forward motion of the tibia.
The posterior cruciate ligament is the strongest ligament. It proceeds from a posteromedial, paracentral location and inserts behind the anterior cruciate paracentrally and slightly laterally. It prevents backwards motion of the knee.
The medial collateral ligament (aka tibial collateral ligament) attaches the medial side of the femur to the medial side of the tibia and limits sideways motion.
The lateral collateral ligament (aka fibular collateral ligament) attaches the lateral side of the femur to the lateral side of the fibula and limits sideways motion as well.
The collateral ligaments prevent the knee from moving too far side-to-side.
The patellar ligament attaches the patella to the tibia and also helps in stabilization.
The ilio-tibial band is a belt like fascia that runs along the lateral aspect of the thigh from the ilium down to the tibia which prevents excessive lateral movement of the knee.
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