Range of motion of the knee is the range in degrees through which the knee can bend and straighten, and which is normally -5° to +143° in women and -6° to +140° in men.
Page updated October 2023 by Dr Sheila Strover (Clinical Editor)
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.
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.
This video explains the terminology -
Measuring knee ROM with a goniometer
A plastic goniometer with longer arms is usually used to measure the range.
The scale part of the goniometer is placed on the joint line.
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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Measurement of ROM -
- Patellar mobilisations
- Lying wall slides
- Assisted flexion
- Low load prolonged stretching
- Passive extension
- Early knee exercises - visual chart
Peer-reviewed paper -
- 2001 - Motion loss after ligament injuries to the knee - Author: Millett PJ et al. - summarised by Dr Sheila Strover (Clinical Editor)