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  • Anatomy 101: ACL/PCL

Anatomy 101: ACL/PCL

  • by Admin
  • May 9, 2018

For the last couple of months, I have been discussing the knee joint and what happens to it during flexion and extension.

The thing is is that I cannot leave the knee and talk about the supporting cast inside the joint (the guys that hold the knee together). These are four ligaments that form either an M or a W (depends on what school you went to, I learnt it as a W) and they are:

  • Anterior Cruciate Ligament (ACL),
  • Posterior Cruciate Ligament (PCL),
  • Medial Collateral Ligament (MCL), and
  • Lateral Collateral Ligament (LCL)


The Anterior Cruciate Ligament (ACL) is a ligament that connect the femur (thigh bone) to the tibial plateau (shin). Its connection starts at the posterior aspect of the femur and joins into the anterior aspect of the tibial plateau. Its purpose is twofold:

  • It prevents forward “shearing” of the femur against the tibia during knee flexion, and
  • It prevents medial rotation of the femur against the tibia [1]

The Posterior Cruciate Ligament (PCL) is a ligament that also connects the thigh bone to the shin bone in the medial (center) of the joint. Its connection starts at the anterior aspect of the femur and connects to the posterior aspect of the tibial plateau. Its purpose is also two-fold:

  • It prevents the femur from sliding off the anterior edge from the tibia, and
  • It prevents the tibia from displacing posterior to the femur [2]

These two ligaments when looked at from the front or the back of the knee look like they form an X
The Medial Collateral Ligament (MCL) is a ligament that also connects the thigh bone to the shin, but this connection is on the medial aspect of the knee joint (inner part of the knee, please refer to the picture above). Its connection starts at the upper part of the medial (inner) epicondyle of the femur and connects to the medial part of the tibial plateau. Its purpose is to resist forces that would push the knee medially.
The Lateral Collateral Ligament (LCL) is a ligament that once again connects the thigh bone to the shin, this connection is on the lateral aspect of the knee joint (outer part of the knee). Its connection starts at the upper part of the lateral (outside) epicondyle of the femur and connects to superior aspect of the fibula. Its function is to resist forces that would push the knee laterally.
Now I hope that you can see the importance of this specific structure after we analyzed what happens during a squat. These ligaments need to be able to do their jobs properly so that the forces from the squat can extend down into the shin and be used properly. And that pretty much covers the knee. In the next couple of weeks, we are going to get into the hip for a few weeks and look at what happens there.


Tags: ACL PCL

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