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.
Video
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.
Quick links
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Measurement of ROM -
Stiffness -
ROM exercises:
- Patellar mobilisations
- Lying wall slides
- Assisted flexion
- Low load prolonged stretching
- Passive extension
- ERMI
- 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)