MCL injury: causes, diagnosis and prevention

MCL injury refers to an injury of the medial collateral ligament (MCL) in your knee and is usually caused by a one-off trauma, as opposed to overuse. It is the most commonly injured ligament in the knee and is often injured when playing sports, such as football and rugby. 

Your MCL is one of several ligaments in your knee that helps keep it stable and, alongside your lateral collateral ligament, controls the sideways movement of your knee. Consequently, when injuring your MCL, it is also common to injure one of the cruciate ligaments in your knee and/or one or both of the two C-shaped pieces of fibrous cartilage in your knee joint called menisci.

MCL injury symptoms

On injuring your MCL you may hear a popping sound, feel immediate sharp pain on the inner side of your knee and notice immediate swelling on the inner side of your knee.

Other symptoms of an MCL injury include: 

• Bruising, especially on the inner side of your knee
• Feeling as if your knee is about to give way 
• Instability or looseness in your knee, especially when pivoting or going up and down stairs
• Pain and tenderness on the inner side of your knee
• Stiffness that makes it difficult to move your knee

What causes an MCL Injury?

The MCL is most often injured by a direct blow to the knee that pushes the knee inwards towards the other knee.

Most common causes of MCL tears

The sudden movement of one knee inwards, which damages the MCL, most often occurs while playing sports, such as during:

• A cutting manoeuvre when you firmly plant one foot down and change direction
• A football tackle that causes a direct blow to the outer side of the knee
• A hyperextension of the knee eg when skiing
• An awkward landing when jumping eg when playing volleyball
• Squatting or lifting heavy objects eg when weightlifting

Although MCL injuries are usually caused by a one-off trauma, they can also be caused by repeated strain on the knee that wears out the ligament. 

Diagnosis of inner knee pain

Your doctor will ask about your symptoms and when they started, as well as whether you were doing something in particular when the pain started eg playing football. They will then perform a physical examination to check for swelling and tenderness. They may also ask you to move your knee to check its range of motion. This will help determine if the MCL and/or any other ligaments or menisci are injured.

This may be enough to diagnose an MCL injury. However, in some cases, you may need further tests, such as scans, to diagnose an MCL injury and/or determine how severe it is.

Diagnostic imaging

To diagnose an MCL injury and/or determine how severe it is, your doctor may recommend you have a scan, such as: 

• An X-ray — this uses low levels of radiation to capture images of your bones; an X-ray can’t detect an MCL injury but can rule out other injuries that produce similar symptoms
• MRI scan — this uses strong magnets and radiofrequency energy to create detailed images of your soft tissues; an MRI scan can identify the location of an MCL injury and how severe it is
• Ultrasound scan — this uses high-frequency sound waves to create images of the inside of your body

How do you treat an MCL Injury?

Treatment for an MCL injury varies according to how severe it is. 

In the first instance, you should rest your knee and avoid bearing weight on it. Keep it elevated on a cushion whenever possible and apply a cold compress for up to 20 minutes three to four times a day. Avoid drinking alcohol and running, and do not apply heat to your knee or massage it. 

You may need further treatment, such as knee bracing, physiotherapy, medication, and, in more severe cases, surgery. 

Medicine for MCL Injury

To relieve your knee pain, you can take over-the-counter painkillers eg paracetamol or ibuprofen. If your knee pain is severe, your GP may prescribe stronger prescription painkillers. 

Physiotherapy for MCL Injury

A physiotherapist will examine your knee and its range of movement. They will then put together an exercise programme to rehabilitate your knee. This will help restore its full range of motion, strength and stability.

Surgery for an injured MCL

In most cases, surgery isn’t needed to treat an MCL injury. However, if other ligaments in your knee, in addition to your MCL, are damaged or your knee continues to be unstable after physiotherapy, you may need surgery.

MCL injury recovery time

Depending on how severe your MCL injury is, it can take between several days and eight weeks to recover. 

MCL injuries are graded, with each grade having an average recovery time as follows: 

• Grade I MCL injury ie a sprain or overstretched MCL — it usually takes several days to a week to recover fully 
• Grade II MCL injury ie a partial or incomplete tears — it usually takes two to four weeks to fully recover
• Grade III ie a complete tear — it usually takes four to eight weeks to fully recover

If you have a grade III MCL tear and another injury to your knee eg another ligament is damaged, it can take more than eight weeks to fully recover and you may need surgery.