The knee joint is made up of four ligaments: the ACL, MCL, PCL, and LCL. The LCL (lateral collateral ligament) connects the femur to the fibula and prevents excessive side-to-side movement of the joint. It is located on the outside of the knee joint.
Your LCL can become injured when your knee bends too far inwards. An LCL tear is most commonly the result of a sports injury or other traumatic injury like a fall. LCL injuries, and all other ligament injuries are diagnosed according to a graded scale. Grade I is the least severe, and Grade III is the most severe.
- Grade I LCL Tear – You will feel some pain and pressure on the outside of the knee with a grade I LCL tear. The ligament is only slightly torn, so you may be able to walk on it.
- Grade II LCL Tear – A grade II LCL injury is an incomplete tear and may cause some instability in the joint when you pivot. Pain and swelling of the knee are common with a grade II tear.
- Grade III LCL Tear – A grade III LCL injury is a complete tear of the ligament, which may be combined with injuries to the cruciate ligaments (the ACL and MCL). A grade III LCL tear causes pain, swelling, and difficulty bending the knee. This type of injury typically requires surgery.
Diagnosing LCL Injuries
When you injure your knee, your doctor will perform a thorough physical examination to determine if you have a ligament tear. An MRI is then needed to determine the grade of the injury and to see if any other ligaments have been torn in conjunction with the LCL.