Lateral Collateral Ligament Injury

The LCL is one part of a group of structures at the back and outer side of the knee called the posterolateral corner. LCL injuries are often associated with injuries to other ligaments, most often the anterior cruciate ligament (ACL) or posterior cruciate ligament (PCL).^[1]

How is an LCL injury graded?

LCL injuries are graded by how much of the ligament is damaged and how loose the knee feels when it is examined:

• Grade 1: the ligament is stretched, with a few fibres torn. The knee stays stable.
• Grade 2: the ligament is partly torn. The knee opens a little more than normal on the outer side when it is tested, but there is still a firm end point.
• Grade 3: the ligament is completely torn. The knee is unstable on the outer side. Grade 3 tears are more likely to come with injuries to the rest of the posterolateral corner or to the cruciate ligaments.^[3]

The grade on an MRI scan does not always match how loose the knee feels on examination,^[2] so treatment depends on both.

What causes a lateral collateral ligament injury?

The LCL is injured when a force pushes the knee outwards, for example:

• A blow to the inner side of the knee, such as a tackle in football or rugby.
• A twist with the foot planted, or the knee being forced straight past its normal range (hyperextension).
• Grappling sports such as wrestling and jiu-jitsu.
• A car accident or a bad fall, which can tear several ligaments at once (a multiligament injury).

If you are naturally bow-legged (varus alignment), more load passes through the outer side of your knee. This puts extra strain on a healing or reconstructed LCL.^[4]

What are the symptoms of a lateral collateral ligament injury?

Symptoms depend on the grade and on whether other structures are hurt. They can include:

• Pain and tenderness on the outer side of the knee.
• Swelling, which is often milder than with a cruciate ligament tear.
• A feeling that the knee is loose or gives way when you turn or step sideways.
• After a severe injury, the knee bowing outwards when you walk.

When should you see a doctor?

See a doctor promptly if:

• You cannot put weight on your leg, or the knee looks out of shape.
• Your knee gives way or feels unstable after the injury.
• The swelling is large or comes on within a few hours.
• You have numbness on the top of your foot, or you cannot lift your foot or toes (foot drop).

Numbness or foot drop can mean the peroneal nerve, which runs past the outer side of the knee, has been stretched. This needs urgent assessment.

How is a lateral collateral ligament injury diagnosed?

Your doctor will ask how the injury happened and examine both knees, checking how far the outer side of the knee opens compared with the other side, and testing the posterolateral corner and cruciate ligaments. Imaging usually includes:

• X-rays to look for a small piece of bone pulled off the top of the fibula. A standing X-ray of the whole leg shows your alignment.
• Stress X-rays, taken while the knee is gently pushed open, to measure looseness.
• MRI to show the ligaments and cartilage. A complete LCL tear on MRI is a strong sign of wider instability at the corner.^[3] But MRI misses or misgrades some injuries on the outer side of the knee.^[5]

How is a lateral collateral ligament injury treated without surgery?

Most grade 1 and 2 LCL injuries heal without surgery. The aim is to protect the ligament while it heals, then rebuild strength. No trials have compared rehabilitation programs for the LCL, so treatment follows the pattern used for other knee ligament sprains.

Protecting the knee

Rest, ice and keeping the leg raised help settle pain and swelling in the first days. You may need crutches for a short time, and simple pain relief from your pharmacist or GP can help.

Brace

A hinged knee brace supports the outer side of the knee and lets it bend while the ligament heals. It is mostly used for grade 2 injuries.

Physiotherapy

A physiotherapist will help you regain full movement, then strengthen the thigh, hip and calf muscles and retrain balance. Running and change-of-direction drills are added as the knee settles.

Returning to sport

Return to sport depends on how your knee performs, not a fixed date. In a series of 55 professional athletes with isolated LCL injuries treated without surgery, all returned to their previous level of sport, at a median of 76 days (about 11 weeks).^[2] Most had grade 1 injuries and full-time support, so recovery may take longer for others.

When is surgery considered?

Surgery is considered when the LCL is completely torn and the knee stays unstable, or when the tear is part of a wider posterolateral corner or multiligament injury. Rebuilding the ligament with a tendon graft (reconstruction) is usually preferred to stitching the torn ends (repair). In a review of 12 studies of 288 patients, repairs failed in about 1 in 5 and reconstructions in about 1 in 14.^[6]

The alignment of your leg also shapes the plan. If you are bow-legged, a reconstruction on its own is more likely to stretch out, and correcting the alignment with a realignment osteotomy may be advised first or at the same time.^[4] In some people with long-standing instability and bow legs, correcting the alignment is enough on its own, and a ligament reconstruction is not needed.^[7]

What is the outlook for a lateral collateral ligament injury?

The outlook for grade 1 and 2 injuries is good. In the athlete study above, no one stopped playing because of the LCL injury.^[2] Recovery is slower and less predictable after a complete tear, or when the posterolateral corner, the cruciate ligaments or the peroneal nerve are also injured.

References