The lateral collateral ligament (LCL) is a thin band of connective tissue that runs along the outside of the knee. It connects the femur to the fibula and stabilizes the knee, bracing it from unusual impact. However, injuries are common, particularly during contact sports.

Injuries to the LCL, such as sprains and tears, can cause symptoms such as weakness in the knee, pain, and swelling. Injuries are typically more common in athletes who participate in contact sports that put stress on the knee, such as football or soccer. Treatment for an LCL injury will largely depend on factors such as how severe the injury is and the person’s general health.

In this article, we will discuss what the LCL is, how common LCL injuries are, treatments, and recovery timelines.

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The LCL is a band of connective tissue called a ligament. It runs along the outside of the knee and connects the femur (thigh bone) to the smaller bone (calf bone) in the lower leg, called the fibula.

The inside of the knee has a similar ligament, the medial collateral ligament (MCL). Together the collateral ligaments help to stabilize the knee. They control the movement of the knee from side to side and help protect against unusual or odd movements the joint should not make.

Click here to learn more about the anatomy of the knee.

Th LCL plays an important role in stabilizing the knee. Activities that put stress on this ligament, such as bending, twisting, or quickly changing direction, may lead to injuries of varying degrees. While injuries typically occur from sports where forceful collisions are common, people may also injure the LCL following a car accident, fall, or another event that impacts the area.

Doctors may refer to an injured ligament as a sprain, and classify them in three grades, or levels of severity. These include:

  • Grade 1 sprain: Minor damage slightly stretches the ligament, but still allows it to stabilize the knee. People will likely experience some tenderness and pain at the point of injury.
  • Grade 2 sprain: Damage stretches the ligament and causes a noticeable looseness in the knee. People will likely experience major pain, tenderness, and swelling of the knee. Doctors may also refer to a grade 2 sprain as a partial tear.
  • Grade 3 sprain: Damage completely severs the ligament into two pieces and causes the knee joint to lose stability. People will experience considerable pain, tenderness, and swelling in the knee. Doctors may refer to a grade 3 sprain as a full or complete tear.

The knee is a complex joint with many delicate parts. Following a LCL injury, instability of the knee can increase the risk of injury to other parts of the knee and leg.

Anything that puts force on the LCL may put the person at risk for an LCL injury. Injuries may be more likely to occur when a force or impact pushes the knee sideways or in a direction it should not move. With enough force, this can result in an injury to the stabilizing structures in the knee such as the collateral ligaments.

Contact sports are a common source of injury. A 2013 article notes that roughly 8% of knee injuries from sports solely involve the LCL. Sports that are more likely to result in LCL injuries include:

  • football
  • soccer
  • gymnastics
  • volleyball
  • basketball
  • baseball/softball
  • lacrosse
  • swimming and diving
  • tennis

A 2020 study notes that isolated collateral ligament injuries are rare. Due to complexity of the knee, injuries are more likely to involve other structures in the knee. It also notes that LCL injuries are not as common as injuries to the other collateral ligament, the MCL.

While 40% of LCL injuries are due to contact sports, other causes may include:

  • motor vehicle accidents
  • falls
  • trauma to the knee

Risk factors for LCL injuries include:

  • being female
  • playing high contact sports
  • playing sports that require velocity in pivoting or turning, and putting pressure on the knee

A person with an LCL injury will typically experience sudden pain on the outside of the knee after a traumatic event to the area, such as a blow to the knee, sudden twist, or a fall.

Other symptoms of an LCL tear can include:

  • stiffness and difficulty moving the knee
  • swelling and tenderness on the outside of the knee
  • bruising
  • feeling that the knee is unstable, may lock up, or will give out when putting weight on it

Doctors can diagnose an LCL injury by first doing a physical exam and asking the person about the event that led to the symptoms.

They may ask specifics about the event, such as where the blow came from, how the person fell or twisted the leg, or other specifics. They may ask the person to move the knee or move the knee themselves and look for other signs of damage and swelling.

Doctors may order imaging tests such as X-rays or MRI scans to look at the tissues and structures inside the knee to decide what type of treatment the person requires.

Treatment will vary based on the structures involved in the injury and the severity. For most LCL injuries, doctors may recommend home care, and advise tips such as:

  • resting and elevating the knee as much as possible
  • using splints, braces, or crutches to protect the knee when moving
  • compressing the area with an athletic wrap
  • using prescription or over-the-counter pain relievers and anti-inflammatory medications
  • applying ice or cold pack to the area regularly to reduce swelling and pain
  • being less active and performing gentle stretches

A physical therapist may work with the person to help regain strength and range of motion in the knee’s surrounding muscles.

More severe injuries or those that include other structures in the knee may require surgical treatments. This may involve repairing, joining, or reconstructing severed ligaments.


Minor sprains may heal quickly with proper home care. While there is no definitive timeline in each case, wearing a brace for a few days may allow the LCL to heal and swelling to go down. The person may be able to start strengthening exercises within a week if their symptoms heal enough to allow for rehabilitation.

Healing is a very personal process based on the injury, and it may take weeks to fully recover. Recovery also depends heavily on other areas of injury and their treatment. If other structures suffer damage and the person requires surgery, it may take people roughly 8–12 weeks to recover.

Returning to sports

Once strength and range of motion return, doctors may clear the person for a slow, progressive return to sports. This may include starting with light activity such as jogging or walking upstairs, and progress back to playing the sport.

The exact timing of this will vary. A 2016 case study of a student athlete with a grade 3 LCL tear notes that the athlete was able to return to competitive sports after 12 weeks of physical therapy. If other structures have damage and require surgery, rehabilitation will take longer.

There is no specific exercise to help heal an injured LCL, but once healed doctors may recommend rehabilitation for the LCL. During rehabilitation, a physical therapist will work directly with the person, giving them exercises and showing them correct form for each. Some knee-strengthening exercises may include:

  • squats
  • leg lifts
  • wall squats
  • knee flexion
  • leg raises
  • leg dips
  • hamstring curls
  • quadricep stretches
  • heel slides
  • hip adduction
  • hip abduction
  • lateral step ups

Preventing an LCL injury may not be possible in every case, as they may occur from accidents or as a result of forces a person cannot control themselves. Taking some precautions may help prevent the injuries that are preventable. Some general tips may include:

  • regularly stretching the entire body to maintain range of motion and ensure proper movement
  • strengthening the legs to help reduce impact on the joint
  • practicing correct movement techniques during lifting and sports

The LCL runs along the outside of the knee and helps stabilize the joint. Impacts or sudden twists from sports or other sources of trauma may cause varying degrees of injury to the ligament. Treatment and recovery times will vary widely based on the type of injury and all of the structures involved.

Minor injuries may not cause any long-term damage. Working with a physical therapist may help strengthen the area and return range of motion as fast as possible after injury.