MCL tear

Inner knee pain after a sudden twist, impact or change in direction can be a sign of a medial collateral ligament (MCL) sprain. This common knee ligament injury can disrupt your daily life, work and athletic activities, but most people recover fully with the right care and guidance.

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Illustration of a human knee joint with labeled parts including quadriceps, femur, patella, and ligaments.

Anatomy of the knee

The medial collateral ligament (MCL) is a strong band of tissue located along the inner side of the knee. It connects your thighbone (femur) to your shinbone (tibia) and plays a key role in keeping your knee stable. The MCL prevents the knee from bending inward and helps protect the joint during walking, running, pivoting and sudden directional changes.

Because the MCL sits along the inner knee, it's exposed to forces from the outside of the joint. This makes it particularly vulnerable to injury during contact sports and other high-impact activities.

Overview

Symptoms

An MCL sprain can range from mild discomfort to significant pain and instability. You may notice:

Tenderness and pain along the inner side of the knee
Swelling or bruising around the joint
Knee stiffness or reduced range of motion
Difficulty walking or bearing weight
A feeling of looseness or instability in the knee

In more severe cases, fluid or bleeding within the joint can add to the swelling and discomfort. Symptoms often reflect the severity of the sprain, so a physical exam can help determine how serious the injury is.

Causes

MCL sprains most often happen when a force pushes the outside of the knee inward, stretching or tearing the ligament. Common causes include:

Direct contact during sports such as football, rugby or soccer
Sudden twisting or pivoting movements
Rapid changes in direction
Less commonly, awkward landings or knee hyperextension

These injuries can affect athletes and non-athletes alike, often happening during everyday activities as well as sports.

Risk factors

Certain factors can raise your risk of an MCL sprain, though having one or more of these doesn't mean you'll experience an injury:

Participation in contact sports or activities with frequent pivoting
Previous knee ligament injuries
Muscle imbalances or weakness around the knee
Improper technique or inadequate conditioning during physical activity

Knowing your risk factors can help you and your care team take steps to protect your knee.

Diagnosis

Diagnosing an MCL sprain begins with a review of your symptoms and medical history, followed by a physical examination to check your knee's movement and stability. Imaging studies may be recommended to confirm the diagnosis and evaluate the extent of the injury, including:

X-rays to rule out fractures or bone injuries
MRI scans to visualize ligament damage and assess surrounding soft tissue

Identifying the grade of your sprain, from mild stretching to a complete tear, helps guide the most effective treatment approach.

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