Diseases & Conditions
Collateral Ligament Injuries
Collateral ligament injuries involve stretching or tearing the ligaments on the sides of the knee. There are two main collateral ligaments:
- The medial collateral ligament (MCL), located on the inner side
- The lateral collateral ligament (LCL), located on the outer side
One of the most common knee injuries is an MCL tear, accounting for up to 43 to 52% of all knee injuries. While the LCL is much less commonly injured (less than 2% of knee injuries), it is still vulnerable to tearing.
Although anyone can injure these ligaments, MCL and LCL injuries are more common in people who engage in activities — such as football, ice hockey, and skiing — that require twisting, direction changes, or direct blows to the knees.
MCL and LCL tears can be treated with surgery or non-operatively. The treatment of your injury will depend on several factors, including:
- The severity of your injury
- Whether you suffered injuries to any other ligaments, such as the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), or meniscus
- Whether your injury is chronic, or long-lasting
Anatomy of the Knee
The knee is made up of four main components: bones, cartilage, ligaments, and tendons.
Bones
Three bones meet to form your knee joint: the femur (thighbone), the tibia (shinbone), and the patella (kneecap). The femur comes from above the knee and meets the tibia, which is below the knee. The kneecap sits in front of the joint.
Ligaments
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:
Collateral ligaments. These are found on the sides of your knee. They control the side-to-side motion of your knee and brace it against unusual movement.
- The medial collateral ligament (MCL) is on the inside. It connects the femur to the tibia.
- The lateral collateral ligament (LCL) is on the outside. It connects the femur to the fibula (the smaller bone in the lower leg).
Cruciate Ligaments. These are found inside your knee joint. They cross each other to form an X, with the ACL in front and the PCL in back.
The cruciate ligaments control the front and back motion of your knee. Most severe MCL tears occur at the same time as ACL tears.
Cartilage
Articular cartilage covers the surfaces of the femur, tibia, and patella. It reduces friction and helps your bones glide smoothly against each other as you move your leg.
Meniscus
Your knee cartilage is cushioned by menisci — rubbery, C-shaped disks that act as "shock absorbers" between the thighbone and shinbone, helping to protect and stabilize the knee joints. Each knee has two menisci — one on the outside of the knee (lateral) and one on the inside (medial).
People who tear their MCL might suffer a meniscus tear at the same time.
Tendons
Tendons connect bone to muscle. They allow for joint movement and provide stability.
Description
The knee is not designed to withstand forces from either side. When you twist too quickly or have a direct impact to the side of your knee, the joint is forced to bend in the wrong direction. This puts enormous strain on the ligaments.
An injured collateral ligament often refers to either:
- Rupturing the MCL or LCL within the ligament itself
- A tear in the bone-ligament connection, meaning the ligament pulls off the bone and may take a small piece of bone with it
The MCL is injured more often than the LCL because the outer knee is more exposed to impact.
Classification of Collateral Ligament Tears
Injured ligaments are classified using a three-grade sprain system based on the degree of injury:
- Grade 1. The ligament is mildly damaged. It has been slightly stretched but is still able to help keep the knee joint stable. The MCL or LCL is intact.
- Grade 2. 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. This type of sprain is most commonly referred to as a complete tear of the ligament. The ligament has been torn in half or pulled directly off the bone. The knee joint is unstable.
Causes of Collateral Ligament Injuries
Injuries to the collateral ligaments are usually caused by a force that pushes the knee sideways and overstresses the ligament.
- Medial collateral ligament tears often occur through direct trauma or sudden changes in direction or speed. The stress on the outside of the knee from these events can strain or tear the MCL.
- Lateral collateral ligament tears are caused by trauma to the inside of the knee, forcing the knee outward and stressing the ligament.
Risk Factors for Collateral Ligament Injuries
- High-contact sports
- Sports with high-velocity pivoting
- Weak lower body strength
- Past knee injuries
Symptoms of Collateral Ligament Injuries
When you injure your MCL or LCL, you might hear or feel a "pop" and you may feel your knee give out from under you. Other symptoms include:
- Pain on the sides of your knee. If there is an MCL injury, the pain will be on the inside of the knee; an LCL injury may cause pain on the outside of the knee.
- Swelling over the site of the injury.
- Instability — the feeling that your knee is giving out.
- Tenderness over the injured side of your knee.
- Stiffness — the inability to fully straighten or bend your knee
Diagnosing a Collateral Ligament Injury
Physical Examination and Patient History
Your doctor will ask you about the following:
- Cause of your injury
- Current symptoms (swelling, clicking, etc.)
- Things you have tried to help with your symptoms (e.g., ice, pain medication)
- Any past injuries to the knee
- Your baseline level of activity
The 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.
Imaging Tests
The doctor will usually order imaging tests to confirm the diagnosis and rule out any additional injuries. These tests may include:
X-rays. Although X-rays do not explicitly show any injury to your collateral ligaments, they can reveal whether the ligament tore off a piece of bone when it was injured.
Stress views (images where the physician applies force to the inside and outside of the knee) are important in younger patients for evaluating whether the growth plate was injured.
Magnetic resonance imaging (MRI) scan. An MRI scan offers the best view of your injured ligaments. It allows the doctor to examine all knee structures (e.g., ligaments, cartilage, meniscus) and offers insight into the severity of the injury.
Treatment of Collateral Ligament Injuries
The treatment for collateral ligament injuries depends on the patient's individual needs, severity of injury, and whether there are other injuries.
Medial Collateral Ligament
If you have a low-grade MCL injury and no related injuries, you can manage your injury non-operatively.
- Treatment is focused on rest, ice, compression, and reducing inflammation with medications.
- You can continue to move around while wearing a hinged knee brace for stability.
- You will also work with a physical therapist to prevent stiffness and rebuilt strength and confidence in the knee.
Lateral Collateral Ligament
Similar to MCL tears, LCL tears can often be treated without surgery. If your LCL injury involves other structures in your knee, your treatment will address those as well.
Non-operative management is an option for LCL tears that are not severe — Grade I and II — and are stable. The patient typically cannot bear weight for 1 week and will use a hinged knee brace to stabilize the knee during recovery. Physical therapy is also critical to regain mobility and strength.
Surgery may be recommended if the ligament has pulled directly off the bone or if you have other injuries along with the LCL tear.
Return to Sports After a Collateral Ligament Injury
After initial management following the injury, the focus of your care will shift to restoring your prior level of activity. This can be achieved by consistently working with a physical therapist.
Once you have regained your range of motion and strength, your doctor may allow functional progression. This is a gradual, progressive return to sports activities. Depending on the severity of your sprain, your doctor may suggest wearing a knee brace during sports activities to prevent re-injury.
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