PhysioWorks News & Tips: Knee Pain, Is It A Ligament?

The knee is a strong but complex joint. It helps you walk, run, jump... and sometimes twist or fall. Four key ligaments keep your knee stable. When one of them is overstretched or torn, it can cause pain, swelling, and difficulty moving.

The Four Main Ligaments in the Knee

Your knee has four major ligaments that work together to support and stabilise the joint:

ACL (Anterior Cruciate Ligament) - prevents the shin bone from sliding forward
PCL (Posterior Cruciate Ligament) - prevents the shin bone from sliding backward
MCL (Medial Collateral Ligament) - stabilises the inner side of the knee
LCL (Lateral Collateral Ligament) - stabilises the outer side of the knee

1. ACL: Forward Stabiliser

What it does: Keeps the knee steady during forward motion and twisting.

Common causes of injury: Sudden stops, changes in direction, or awkward landings common in sports like soccer, basketball, or skiing.

What it feels like:

A popping sound or sensation
Fast swelling
Instability or knee “giving out”
Difficulty putting weight on the leg

Treatment: Depends on severity. Mild injuries may heal with rehab and bracing. More serious ACL tears often need surgery followed by physical therapy.

2. PCL: Backward Stabiliser

What it does: Prevents the shin bone from moving too far backward.

Common causes of injury: A blow to the front of the knee (e.g., hitting a dashboard in a car crash or falling on a bent knee).

What it feels like:

Mild swelling
Pain when walking or going downstairs
Knee may feel unstable

Treatment: Many PCL injuries heal with rest, a brace, and physical therapy. Surgery is only needed in more serious or complex cases.

3. MCL: Inner Protector

What it does: Keeps the inside of your knee stable.

Common causes of injury: A hit to the outside of the knee, pushing it inward, often seen in football or skiing accidents.

What it feels like:

Pain along the inner knee
Swelling
Instability or a loose feeling

Treatment: Most MCL injuries don’t need surgery. Rest, a knee brace, and rehab usually lead to full recovery.

4. LCL: Outer Support

What it does: Stabilises the outer side of the knee.

Common causes of injury: A force that pushes the knee outward, or a sudden twist. These injuries are less common.

What it feels like: