Anatomy of the Lateral Collateral Ligament (LCL)

The lateral collateral ligament, or LCL,  is also called the fibular collateral ligament, or FCL.  It is located on the outside part of the knee.  It prevents one’s knee from swinging side-to-side and is a very important stabilizer to protect other knee ligaments. Unfortunately, the LCL is commonly torn in skiing and we see dozens of these injuries every ski season.

The lateral collateral ligament is one of the main structures of the outside part of the knee.  This part of the knee is called a posterolateral corner of the knee.  The LCL is important to prevent one’s knee from gapping on the outside as well as rotating to the outside.  In the past, posterolateral corner injuries were considered devastating injuries, but newer research, primarily carried out by our lab in Vail, in cooperation with our colleagues at the University of Oslo, has resulted in a significant improvement in the treatment of these injuries.

How to Diagnose an LCL Injury

When one does sustain a lateral collateral ligament tear, the physical exam is often a defining moment as to the next form of treatment.  When there is significant gapping, one has to compare it to the normal contralateral knee.  This is because some patients can have an increased amount of gapping and just be normally loose in their overall joint mechanics.  Our lab has found that stress x-rays are the best way to diagnose a LCL tear and should be performed whenever there is concern about there being some increased gapping in the outside of the knee.  The magic number that is consistent with a complete LCL tear is between 2.0 and 2.7 mm, so it is important to obtain stress x-rays on both knees to see the difference in side-to-side opening.

Most LCL tears occur in combination with an ACL or PCL tear.  Thus, it is essential to diagnose the combined LCL tear with the obvious ACL or PCL tear in these circumstances.  This is because the lack of an LCL has a high risk of causing an ACL or PCL reconstruction graft to stretch out and fail if it is not treated.  Unfortunately, an LCL tear is fairly common in skiing injuries so being aware of this potential injury is important to making sure one has the best overall outcome and that the ACL reconstruction does not fail.

When one is found to have a complete LCL tear, one should proceed to surgery.  The best outcomes are obtained in the first few weeks after injury.  Compared to the other side of the knee with the MCL, LCL tears rarely heal, so one should have surgery sooner rather than later.

How to Treat an LCL Injury

The best surgical procedures for LCL tears are reconstructions.  This has been documented in the peer-review literature.  Repairs have a much higher risk of failure and should only be considered in very specific circumstances.  The reconstruction that we developed using a hamstrings graft placed in the normal position of the LCL on the thigh bone (femur) and fibula has been documented to have outstanding outcomes and, even when combined with an ACL reconstruction, most athletes get back to full activities after surgery.

Recovery After LCL Surgery

After surgery, we start physical therapy on the first day postoperatively.  This is important because when one does have a combined LCL and ACL tear, the violent injury to the knee often means that the meniscus is also damaged and had to undergo a concurrent repair.  Therefore, knee motion is important on the first day after surgery and we allow flexion to 90 degrees.  We have performed some recent clinical trials looking at an early weightbearing program for the combined ACL and LCL tear and this study should be published in the near future.

All in all, when one does sustain a complete LCL tear, surgery consisting of an LCL reconstruction should be indicated in almost all patients.  While this injury almost always occurs in combination with other knee ligament injuries, especially with an ACL tear,  the postoperative outcomes are very good and restore most athletes back to full competition.  When one does have a combined LCL and other knee ligament surgery, combining the surgery with a good physical therapy regimen is important to minimize the risk of stiffness and to get you back to full activities.

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