Knee ligament sprains or tears are a common sports injury.
Your knee ligaments connect your thighbone to your lower leg bones. The medial collateral ligament (MCL) and lateral collateral ligament (LCL) are found on the sides of your knee.
Athletes who participate in direct contact sports like football or soccer are more likely to injure their collateral ligaments.
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.
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.
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.
During your first visit, your doctor will talk to you about your symptoms and medical history.
During the physical examination, your doctor will check all the structures of your injured knee, and compare them to your non-injured knee. Most ligament injuries can be diagnosed with a thorough physical examination of the knee.
Other tests which may help your doctor confirm your diagnosis include:
X-rays. Although they will not show any injury to your collateral ligaments, x-rays can show whether the injury is associated with a broken bone.
Magnetic resonance imaging (MRI) scan. This study creates better images of soft tissues like the collateral ligaments.