Extension

A normal range of motion (ROM) at the knee includes flexion, extension and a small amount of hyperextension. When the knee is straight it is said to be extended. 

Full extension of the knee is generally quoted as 0 degrees but may normally be as much as -6 degrees, which is very slightly bent backwards.

Is it important to regain full knee extension?

After injury or surgery it is more important to regain full extension of the knee than it is to regain full flexion.

What causes knee extension loss?

There may be a number of reasons why one struggles to regain knee extension after a knee insult:

• inhibition of the quadriceps muscle
• wasting of the quadriceps muscle
• contracture of the hamstrings muscle
• an obstruction in the joint line
• adhesions in the normally-mobile soft tissues around the front and back of the knee
• adhesions that have turned to scar tissue (arthrofibrosis)

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Active extension exercises

Active extension exercises rely mostly on the quads muscles, but these muscles often become inhibited after knee injury or surgery, and it may take time to get the muscle to start triggering.

Usually an extension exercise regime begins with 'short arc extensions' from a seated position.

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What is passive extension?

Passive extension exercises, such as 'prone hangs' use gravity to help regain extension.

A 'drop-out cast' allows the clinician to gradually improve extension within a plaster-of-Paris that has been windowed to allow serial wedges to be placed under the heel.

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Other relevant links

Prone hangs, Passive extension, Drop-out cast, Short arc extensions, Range of motion, Quadriceps lag, Knee extension device

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Forum discussions

• The 1% group who never regain full R.O.M. - Patients compare notes about regaining range of motion.

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