What is the FCL?
The lateral collateral ligament (LCL), also called the fibular collateral ligament (FCL), is located on the outside of the knee and connects the upper leg bone to the lower leg bone called the fibula. It is one of the four critical ligaments that stabilize the knee including the anterior and posterior cruciate ligaments and the medial and lateral collateral ligaments. The FCL ligament functions to stabilize the knee during side to side motion.
Injuries to the FCL
Isolated injuries to the FCL are rare and are commonly found in tennis and gymnastics. Most FCL injuries are associated with damage to multiple ligaments including the anterior cruciate ligament (ACL), and the posterior cruciate ligament (PCL).
The FCL is part of the Posterolateral corner (PLC). The PLC is a secondary knee stabilizer complex that contains the FCL, and another ligament (PFL) and a tendon (PT). Any of these structures can also be damaged and must be repaired or replaced.
What causes FCL injuries?
Knee ligaments are injured on the side of the knee opposite of the location of the trauma. When the impact is on the outside of the knee, the ligaments on the inside of the knee are injured. Conversely, if the impact is on the inside of the knee, damage is done to the outside knee ligaments such as the FCL.
FCL injuries are commonly caused by a direct blow to the inside of the knee; by twisting injuries of the knee; in sports such as soccer, basketball, skiing, football and hockey that require quick changes in direction or violent collisions; and from a fall or awkward landing from a jump. The FCL is more flexible than other ligaments and can be injured by repetitive stress that causes the ligament to stretch and become loose.
What are the symptoms of an FCL injury?
Common symptoms include:
- Pain and swelling along the joint line on the outside of the knee
- Knee instability with extension
- Stiffness, soreness, tenderness, bruising on the outside of the knee
- Catching or locking in the knee with movement
- Numbness and weakness in the foot if the tear is severe and the nerve near the ligament is compressed.
How is an FCL Injury diagnosed?
Dr. Cooper will ask about how your injury occurred and your symptoms. He will conduct a physical exam of the knee and test range of motion and other tests and will order an x-ray to rule out broken bones, and an MRI to reveal the damage including ligament tears. Dr. Cooper will focus on the health of the PLC, to assure any additional injuries are promptly treated.
Grading the injury
- Grade one is a sprain. The ligament is stretched causing tenderness and micro tears of the ligament. It is treated with conservative measures.
- Grade two is a partial tear or serious stretch which causes significant pain, tenderness and swelling, and obvious looseness of the knee. A partial tear may heal on its own with conservative measure plus physical therapy.
- Grade three is full rupture or tear that makes it difficult to bear weight on the knee. It causes considerable pain and tenderness and may involve an injury to the ACL and/or the PLC as well. When the FCL is completely torn, it usually cannot heal alone. Instead, surgery to reconstruction the ligament will be the treatment of choice.
FCL reconstruction surgery
Grade three tears will require surgical reconstruction. However, if there are injuries to the other structures in the PLC they must be treated as well or can cause chronic pain and instability and result in surgical failure of FCL repair alone. Therefore, reconstructive and repair surgery will be required for all damaged knee structures to ensure return to function.
Reconstruction will involve replacing the torn ligament with a graft of tissue, usually a tendon, either from the patient (autograft) or a donor (allograft). If other ligaments are damaged, they will be repaired or replaced during FCL reconstruction.
Full recovery dependS on the extent of repairs, and begins with immediate physical therapy.
