Collateral Ligament Injury (MCL, LCL, UCL)

What the collateral ligaments do

Collateral ligaments are strong bands on each side of a hinge joint. They keep the joint stable when force pushes it sideways.

Grades of injury

• Grade 1: the ligament is stretched with microscopic tears. Tender, but the joint is stable.
• Grade 2: partial tear. More pain and swelling, slight looseness.
• Grade 3: complete tear. The joint opens up when stressed sideways; pain may be less than expected because the fibers are fully torn.

Knee collateral ligament injuries

MCL injury

An MCL injury causes pain on the inner side of the knee, tenderness along the ligament, swelling, stiffness and sometimes a sense the knee may buckle. It often occurs in football, soccer, hockey and skiing. Combined MCL and ACL injuries are common, sometimes with a meniscus tear.

LCL injury

LCL tears are less common and usually part of a more complex injury to the outer back corner of the knee (posterolateral corner). They cause pain on the outer knee, instability, and sometimes numbness or foot drop if the peroneal nerve is stretched.

Elbow UCL injury

The elbow UCL is stressed every time a pitcher throws. Repeated strain causes microtears, and eventually a partial or complete tear. Symptoms are pain on the inner elbow during the late cocking or acceleration phase of throwing, loss of velocity, and sometimes tingling in the little and ring fingers. Complete tears in throwers may need reconstruction ("Tommy John surgery").

Thumb UCL injury (skier's thumb)

A fall onto an outstretched hand forces the thumb sideways. The result is pain and swelling on the inner side of the thumb base and a weak pinch. If the torn ligament flips over a tendon (a Stener lesion), it cannot heal by itself and needs surgery. Chronic looseness from repeated strain is called gamekeeper's thumb.

Diagnosis

1. Examination: the doctor applies gentle sideways stress to the joint and compares with the other side to grade the injury, and checks other ligaments, the meniscus, nerves and blood supply.
2. X-rays: rule out fractures and avulsion fragments (where the ligament pulls off a piece of bone).
3. MRI: confirms the grade and detects associated injuries. Ultrasound is useful for the thumb and elbow UCL.

Treatment

Immediate care

• Rest and protect the joint; use crutches if walking is painful.
• Ice for 15 to 20 minutes every 2 to 3 hours for 48 hours.
• Compression and elevation.
• Pain relief: ibuprofen, naproxen or acetaminophen (paracetamol), following the label dose.

Non-surgical treatment

• Knee MCL: most grades 1 to 3 isolated MCL tears heal well without surgery, because the MCL has a good blood supply. A hinged knee brace protects it while allowing bending. Physical therapy restores motion and strength.
• Elbow UCL: rest from throwing, then a structured rehabilitation and throwing program for partial tears. Some partial tears are treated with platelet-rich plasma injections, although evidence is mixed.
• Thumb UCL: a thumb spica cast or splint for 4 to 6 weeks for partial tears.

Surgery

• complete LCL and posterolateral corner injuries
• MCL tears combined with ACL or other ligament injuries, or that remain unstable
• complete elbow UCL tears in athletes wanting to return to throwing
• complete thumb UCL tears, Stener lesions and avulsion fractures that are displaced

Recovery time

Frequently asked questions

What is a collateral ligament injury?

It is a sprain or tear of one of the ligaments on the sides of a joint, most commonly the knee's MCL or LCL, the elbow's UCL or the thumb's UCL. It usually results from a force that pushes the joint sideways.

How long does an MCL injury take to heal?

Grade 1 MCL sprains usually heal in 1 to 2 weeks, grade 2 tears in about 3 to 4 weeks, and grade 3 tears in 6 weeks or more. Associated injuries such as an ACL tear make recovery longer.

Does a torn MCL need surgery?

Usually not. Most isolated MCL tears, even complete ones, heal with a hinged brace and physical therapy. Surgery may be needed when the MCL tear occurs with other ligament injuries, or remains unstable after treatment.

What is skier's thumb?

Skier's thumb is an injury to the ulnar collateral ligament at the base of the thumb, often from falling with a ski pole in the hand. It causes pain, swelling and weak pinch. Partial tears heal in a splint; complete tears often need surgery.