How Are the Ligaments Affected in Total Knee Replacement?

A common question regarding (also known as total knee arthroplasty) is what happens to the ligaments in the knee as a result of knee replacement?

First, it is helpful to understand the location and function of these important soft-tissue structures.  There are four major ligaments in the knee joint.  Two of these ligaments act as “side-to-side” stabilizers in the knee:  the medial collateral ligament (MCL) and the lateral collateral ligament (LCL).  These ligaments connect the femur (thigh-bone) to the tibia (shin-bone).  They are located on the inside (medial) and outside (lateral) parts of the knee.

The other two ligaments, the anterior cruciate ligament and the posterior cruciate ligament (ACL and PCL) limit “front-to-back” or anterior-to-posterior movement of the knee.  These ligaments are named based on their attachment site on the tibia and are found roughly in the middle of the joint.  The PCL runs from the back or posterior part of the tibia to the front of the femur.  The ACL runs in the opposite way.  These ligament cross, hence the name “cruciate”.

So what happens to these ligaments as a result of total knee replacement?   The collateral ligaments (LCL and MCL) are left intact as they are important for proper function and longevity of a total knee replacement since the function of these ligaments is, for the most part, not replaced by the prosthetic components.

The ACL is removed since the portions of the bone where it typically attaches are removed and replaced by the implant components.  Often this structure is severely compromised in patients requiring total knee replacement.

What is done with the PCL is not as straightforward.  Depending on the particular patient as well as surgeon preference, the PCL may either be retained or sacrificed. Implants specific to either scenario are available for the surgeon’s use.

For more on types of implants see our section on this topic.

So in summary, in a standard total knee replacement..

  • The collateral ligaments (LCL and MCL) are preserved
  • The ACL is removed
  • The PCL is either retained or sacrificed.

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