Collateral Ligament Injuries of the Knee

Introduction

The knee is one of the most frequently injured joints in the body. Injuries can occur during sports activities, work activities, or even normal activities of daily life such as walking or going up and down stairs. There are multiple structures that can be injured including the bones, the ligaments, the meniscus cartilage, and the articular cartilage.

Anatomy

There are four main ligaments that provide stability to the knee, while allowing for the motion that occurs with normal activities. On the outside of the knee is the Lateral Collateral Ligament (LCL), and on the inside of the knee is the Medial Collateral Ligament (MCL). In the center of the knee are the Anterior and Posterior Cruciate Ligaments (ACL & PCL).

Mechanism of Injury

The MCL is typically injured when a person is hit on the outside of the knee, and the LCL is injured when the person is hit on the inside of the knee, usually during sports activities. The ligaments can also be injured during a twisting injury. Patients may damage one ligament in a minor injury, or multiple ligaments in a severe injury.

Symptoms

When a ligament is injured, the patient may hear or feel a "pop", or "snap." Sometimes people around the patient may even hear the "pop". As a result of the injury, the patient may fall, and is unable to get up and put weight on the injured leg because of pain. The patient will often have stiffness and limited motion of the knee, along with swelling.

Physical Exam

Following an injury, the knee will generally be swollen, and occasionally the knee may turn black and blue in a few days. The knee may be black and blue on the side of the impact, or it may be on the side of the ligament injury as a result of bleeding under the skin. Patients with extremely swollen knees typically have suffered a severe injury that may include damage to multiple ligaments, or possibly a fracture.

Following the injury, the patient may have very limited motion of the knee. The patient may have tenderness along the MCL or LCL, often with the most tenderness where the ligaments insert on the bone of the femur and tibia for the MCL, or the femur and fibula for the LCL.

Depending on the severity of the injury, the patient may have laxity of the ligament. The degree of laxity may be difficult to assess in an acute setting, due to pain. In severe injuries, a knee dislocation can occur, and it is critical to check the neurovascular status of the leg, to assure that no damage has occurred to the arteries or nerves of the leg.

Diagnostic Studies

Whenever a patient suffers a significant knee injury, x-rays should be obtained to determine whether a fracture, or dislocation has occurred. The proper views should include AP, lateral, tangential, and tunnel views of the knee. Magnetic Resonance Imaging (MRI) can be very helpful in assessing damage to the ligaments of the knee. However, it is rarely necessary to order an MRI scan immediately following an acute knee injury.

Most patients can initially be managed appropriately without an MRI. An MRI can be obtained several days or weeks later to check for damage to the meniscus cartilage, articular cartilage, ligaments, or a fracture that may not be visible on plain x-rays. If a severe injury has occurred, an urgent MRI may be appropriate. If a knee dislocation has occurred, an arteriogram may be necessary to detect damage to the arteries around the knee.

Treatment

The majority of MCL & LCL injuries can be managed non-operatively. As with many orthopedic injuries, the initial treatment includes "RIICE"

• Rest
• Ice
• Immobilization
• Compression
• Elevation

The knee can be wrapped with an ace bandage to minimize swelling, and then an ice bag can be placed on the knee for 15-20 minutes at a time, every 2-4 hours. The patient should be given crutches for walking. It may also be advisable to place the knee in an immobilizer brace, to provide comfort, and facilitate walking. With most knee injuries, it is OK to allow partial weight-bearing in the immobilizer while using the crutches. The patient should be encouraged to remove the knee immobilizer several times a day, and try to bend and straighten the knee to prevent stiffness from developing.

For most patients, the recovery period following a collateral ligament injury lasts between 3 to 6 weeks.

If there is concern of a severe knee injury, it may be appropriate to seek an urgent referral to an orthopedic surgeon, usually within a few days of the injury. Surgery may be indicated in certain patients with these more severe injuries, and those injuries where more than one ligament may be damaged.