Range of motion

 

Terminology of range of knee motion

A straight leg is said to be at zero (0) degrees (ie zero degrees of flexion). Full flexion is normally about 135-143 degrees, depending on the muscle/fat bulk of the limb.

Although a straight knee is at 0 degrees, normally, a person can actually go beyond 0 degrees, and slightly 'hyper-extend', so full extension might be -6 degrees. This is very important in rehabilitation, because the last few degrees of extension are critical for knee stability. So when you are rehabilitation you need to get a measurement of your normal knee - both in flexion and extension - and use that as the desired range for the problem knee.

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Is the range of knee motion different in men and women?

There is generally a difference in ROM between men and women, with women having a slightly greater range than men.

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Video

This video explains the terminology -

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Measuring knee ROM with a goniometer

A 'goniometer' is a circular plastic disc marked out in degrees, with two long arms - one stationary and the other able to move. The centre of the disc is placed on the side of the knee at a bony reference point, and the one arm is pointed at the ankle while the other is pointed at the hip.

Two variants of ROM are usually measured during rehabilitation - the 'active' ROM - ie the range that the patient can achieve unaided, and the 'passive' ROM which is the range that can be achieved if the physiotherapist takes the knee through its motion.

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