Ligaments of the Knee Joint

The movement that occurs between Femur and Tibia is called as Translation in which the Femur glides over the Tibia. During translation, the Knee joint is stabilised by primary as well as secondary restraints. The primary support is provided by various ligaments that attach themselves to one or the other bone of the joint whereas the secondary support comes from capsule & muscles around the joint. Primary support is provided by 5 ligaments as mentioned below:

1. Anterior Cruciate Ligament
2. Posterior Cruciate Ligament
3. Lateral Collateral Ligament
4. Medial Collateral Ligament
5. Coronary Ligament

The location and function of each of these ligaments is given in the following paragraph. The lateral and the medial collateral ligaments are present on either side of the joint to restrict medial-lateral movement between femur and tibia. Lateral collateral ligament (LCL) extends from the lateral side of femur to the lateral side of head of Fibula. Medial collateral ligament (MCL) extends from medial femur to the medial aspect of tibia. Thus, among themselves, these two ligaments take care of medial-lateral stability of the knee joint.

Anterior Cruciate Ligament (ACL) and Posterior Cruciate Ligament (PCL) are the most crucial ligaments of the joint and provide maximum stability to the joint over the entire range of motion of the Knee. These ligaments cross over each other in the Intercondylar notch and hence the name ‘Cruciate’. These ligaments restrict the anterior-posterior movement between tibia and femur. It should be remembered that the femur only glides over the tibia. There is hardly any anterior-posterior or medial-lateral movement. The Anterior Cruciate Ligament has its proximal attachment on the medial aspect of lateral femoral condyle in the roof of the intercondylar notch and extends downwards and medially to insert on the anterior aspect of the medial tibial condyle. The sites of attachment and insertion are very essential for a person selling Arthroscopy products because during ACL reconstruction, the positioning of the graft is the most critical factor in the entire surgery. ACL is more like a cord at its origin but gradually develops into a broader band of fibres towards its insertion. This nature of the ACL is very unique. The Anteromedial part that is more or less like a band is called Anteromedial Band (AMB) while the other part that is more cord-like is called the Posterolateral Bulk (PLB). As mentioned earlier that these two parts behave uniquely, it is important to understand the distinction because during the flexion of knee, AMB is taut and PLB is lax whereas during extension of knee, PLB is taut and AMB is lax. Thus, ACL provides stability to the joint throughout its entire range of motion.

The Posterior Cruciate Ligament has its distal attachment on the posterior aspect of the lateral tibial plateau. It ascends anteriorly and somewhat medially to attach on the lateral aspect of the medial femoral condyle. The function of the PCL is to prevents the femur from sliding anteriorly on the tibia during flexion and the tibia from sliding posteriorly.