A lateral collateral ligament sprain occurs when the ligament on the outer side of the knee tears. This type of sprain is most common in people who play contact sports, such as football.

While knee injuries represent up to 39 percent of all injuries in athletes, lateral ligament injuries are less common. Many lateral collateral ligament (LCL) injuries occur alongside other knee damage.

The LCL connects the thighbone to the smaller calf bone. It controls the sideways movement of the knee, and, alongside the medial collateral ligament on the inner knee, it contributes to knee stability.

In this article, we discuss the causes and symptoms of LCL sprains. We also list some methods of treating and preventing this injury.


Football player with injured knee caused by lateral collateral ligament sprain
Athletes who play contact sports are at risk of an LCL injury.

An LCL sprain usually occurs when the knee pushes out beyond the usual range of motion. This overstretches and tears the ligament.

An LCL sprain may have causes including:

  • direct contact to the inside of the knee, such as in a collision or a tackle
  • poor landing technique
  • suddenly changing direction while running
  • twisting the knee when the foot is stationary

The following groups are more at risk of sustaining an LCL injury:

  • athletes who play contact sports
  • people with weak muscles
  • people with poor coordination

What are the symptoms?

The most obvious symptom is pain, which may be mild or severe, on the outer side of the knee. People sometimes hear a snapping or tearing sound when the injury occurs.

Other symptoms include:

  • bruising to the skin
  • general weakness in the knee joint and a feeling that it may give way
  • numbness in the knee, which may occur due to damage to nerves
  • stiffness
  • swelling along the outside of the knee
  • tenderness around the ligament, especially if with pressure
  • the sensation that the knee is locking during movement

The severity of symptoms depends on the seriousness of the sprain. Doctors categorize LCL sprains as:

  • Grade 1: The ligament overstretches but does not tear. It can result in mild pain or swelling. A grade 1 sprain does not usually affect joint stability.
  • Grade 2: The knee ligament partially tears. Symptoms can include moderate pain, swelling, knee instability, and difficulty using the joint. The skin around the LCL ligament may bruise.
  • Grade 3: This involves a complete ligament tear. Symptoms include swelling, significant bruising, joint instability, and difficulty putting weight on the leg. A grade 3 sprain increases the risk of injury to other parts of the knee and leg.

When to see a doctor

Doctor examining knee with lateral collateral ligament sprain
A doctor may use MRI scans and X-rays to diagnose an LCL sprain.

People with symptoms of a knee injury should see a doctor for diagnosis and treatment. They will typically ask about symptoms and perform a physical examination.

They will look for the following around the LCL:

  • pain
  • swelling
  • tenderness
  • instability

The will also compare the injured knee with the other knee. The doctor may use imaging tests to confirm the diagnosis, including:

  • MRI scans: This displays images of soft tissues in the knee, including the LCL. According to the University of California, San Francisco, MRI scanning is more than 90 percent accurate in evaluating LCL injury severity.
  • X-rays: Initially, a doctor will order an X-ray. This test does not show ligament injuries, but it may help determine whether a broken bone is contributing to symptoms.

Treatment options

Treatments for LCL sprains depend on the severity and presence of other knee damage.

To treat an LCL sprain, people can try the following treatments:

Rest the knee

A doctor or physical therapist may recommend resting the injured leg as much as possible, especially in the days following the sprain. Resting gives the ligament time to heal and the inflammation time to subside.

Apply ice

Applying an ice pack to the outer side of the knee can reduce swelling and pain. Use an ice pack several times daily, as needed, for 15–20 minutes at a time.

Do not apply ice directly to the skin, as it can burn. Elevate the knee to prevent swelling.

Try medication

Over-the-counter anti-inflammatory medications may be beneficial for people with mild to moderate ligament tears. Examples of such medications include ibuprofen (Advil, Motrin IB) and naproxen sodium (Aleve).

A doctor may be able to prescribe stronger pain relief medicines if necessary.

Use a knee support

Some people may benefit from the use of a knee brace, splint, or compression sleeve to stabilize the joint. People with grade 2 or 3 sprains may also need to use crutches for a short period to keep weight off the leg.

Try physical therapy

A program of stretching and strengthening exercises can help people with moderate to severe sprains.

Leg and knee exercises can improve range of motion and strength, as well as help prevent further injury.

Physical therapists may also recommend massage or other treatments to speed up recovery and reduce symptoms.


Grade 3 sprains may require surgery to repair the tear in the ligament.

Surgery is more common in people who have other knee injuries alongside the LCL sprain.

Recovery may take some time, and people will often need to work with a physical therapist to restore full knee function.


LCL sprains are uncommon. It may not be possible to prevent all cases, but the following tips may reduce the likelihood of them happening:

  • Carry out a regular exercise program to stretch and strengthen the structures of the knee and leg.
  • Avoid returning to activities, especially contact sports, too soon following a knee injury.
  • Warm up the muscles thoroughly before playing sports or engaging in other physical activities.

Outlook and summary

The outlook for people with an LCL sprain depends on the severity of the injury.

Grade 1 sprains typically heal within a few weeks. Grade 2 sprains may require longer treatment and rest.

Grade 3 tears have the longest rehabilitation period. It may take several months before a person can return to normal activities. During this time, they will typically need to see a physical therapist and use crutches.

Once a person has regained full range of motion in their knee, and they can walk without difficulty, their doctor may recommend gradually returning to normal activities.