Medial/Lateral Collateral Ligament (MCL/LCL) Sprains
Knee ligaments connect your thighbone to your lower leg bones.
Three bones meet to form your knee joint: your thighbone (femur), shinbone (tibia), and kneecap (patella). Your kneecap sits in front of the joint to provide some protection.
Bones are connected to other bones by ligaments. There are four primary ligaments in your knee. They act like strong ropes to hold the bones together and keep your knee stable.
- Cruciate Ligaments
These are found inside your knee joint. They cross each other to form an “X” with the anterior cruciate ligament in front and the posterior cruciate ligament in back. The cruciate ligaments control the back and forth motion of your knee.
- Collateral Ligaments
These are found on the sides of your knee. The medial or “inside” collateral ligament (MCL) connects the femur to the tibia. The lateral or “outside” collateral ligament (LCL) connects the femur to the smaller bone in the lower leg (fibula). The collateral ligaments control the sideways motion of your knee and brace it against unusual movement.
Because the knee joint relies just on these ligaments and surrounding muscles for stability, it is easily injured. Any direct contact to the knee or hard muscle contraction — such as changing direction rapidly while running — can injure a knee ligament.
Injured ligaments are considered “sprains” and are graded on a severity scale.
- Grade 1 Sprains. The ligament is mildly damaged in a Grade 1 Sprain. It has been slightly stretched, but is still able to help keep the knee joint stable.
- Grade 2 Sprains. A Grade 2 Sprain stretches the ligament to the point where it becomes loose. This is often referred to as a partial tear of the ligament.
- Grade 3 Sprains. This type of sprain is most commonly referred to as a complete tear of the ligament. The ligament has been split into two pieces, and the knee joint is unstable.
The MCL is injured more often than the LCL. Due to the more complex anatomy of the outside of the knee, if you injure your LCL, you usually injure other structures in the joint, as well
Injuries to the collateral ligaments are usually caused by a force that pushes the knee sideways. These are often contact injuries, but not always.
Medial collateral ligament tears often occur as a result of a direct blow to the outside of the knee. This pushes the knee inwards (toward the other knee).
Blows to the inside of the knee that push the knee outwards may injure the lateral collateral ligament.
For more information on symptoms and specific treatment options, visit OrthoInfo.AAOS.org
Adapted from AAOS OrthoInfo