Range of motion

 

Terminology of range of knee motion (ROM)

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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How is knee range of motion measured?

The simplest way to measure range of motion of the knee is with a plastic 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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What is the relevance of knee range of motion?

Sequential measurement of range-of-motion gives you a good idea of how knee rehabilitation is progressing in any one situation.

If the numbers are getting worse it implies that there is a problem with perhaps increasing fluid in the joint, or adhesions in the soft tissues around the joint.

 

• Quote from peer-reviewed paper:

  "Range of motion....is the most important outcome that defines the functional ability after total knee arthroplasty.... A minimum range of knee flexion of 90° is essential to daily activities with about 67° required in swing phase, 83° in climbing stairs, 90° in descending stairs, and 93° in rising from a chair"

  Citation: Sancheti KH, Sancheti PK, Shyam AK, Joshi R, Patil K, Jain A. Factors affecting range of motion in total knee arthroplasty using high flexion prosthesis: A prospective study. Indian J Orthop. 2013 Jan;47(1):50-6. doi: 10.4103/0019-5413.106901. PMID: 23532488; PMCID: PMC3601234.

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Which knee exercises improve ROM?

Any exercise to improve knee ROM needs to be appropriate to the stage of rehabilitation that a patient is in. Pushing the knee too hard early in rehab may lead to inflammation, adhesions and a worsening ROM.

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