Ligament Balancing During Total Knee Arthroplasty

Typically, when your knee is replaced, the goal is to leave your native ligaments alone.

You may have heard of your medial collateral ligament, also known as the MCL, a  commonly injured ligament in sports. The MCL is one of the Cornerstone ligaments of the knee and provides it with most of its external stability after a knee replacement. The MCL ligament is very thick, and like all ligaments, acts like a thick piece of rope connecting bones together. Just like a piece of rope, if there is not enough tension on the ligament, it is very slack and is unable to provide much stability. The converse of this is tightness and extreme strain, leading to pain.

One of the most beneficial aspects of robotic knee replacement is the ability to restore the tension in the ligaments in the knee. During surgery, we can change the tension in the knee by millimeter increments. This can all be done virtually, prior to any actual work on the knee, until the knee is tensioned appropriately. This is largely due to the pre-surgical CT scan that is done, then during surgery the knee is tensioned in several different ways in order for the robot to understand the amount of tension that needs to be restored in the knee. The knee is then virtually replaced on a computer screen using a 3D bone model with the specific ligament tension information to ensure the knee mechanics will be restored properly. Once this is done, the robotic software will lock in the plan, and the robot will perform bony cuts in a very precise manner.

This leads to very reproducible knee mechanics, and in my opinion, much easier rehabilitation and better satisfaction. As in most things in life, balance is key and it is no different with your knee.