Extension: how to estimate it and ways to improve it


Administrative Staff
Jun 11, 2013
United States United States
Review and update June25, 2021

Extension can take a while to return to normal and usually comes after you have accomplished good flexion. Slow, steady progress is important and patience may be required to regain this critical part of your normal range of motion.

By far the best way to regain good extension is to ensure you are walking with the correct "heel-roll to toe" gait and by taking a decent step length (stride). Make sure you are not shuffling because you are nervous of tripping. Don't obsess over this. Just try to make your stride as natural as possible. Use a walking aid (walker, crutches or cane) if you still have even the slightest limp, as that provides you the support you need to take a good, long stride.

Extension is often more difficult to achieve than flexion and can lag behind. The most important thing to remember is that extension is most often blocked by swelling, which is best dealt with by managing the swelling and any pain that may accompany it. If you attempt any extension exercises, be sure you are not doing them to excess as you can irritate tender tissues, increase swelling, and actually make your extension worse.

walking heel toe.jpg

A good extension exercise is to rest your heel on a stool so the knee is unsupported, but do ensure the stool is not too far away from your knee. Mid calf as in this image is about as much as you should use. NEVER just have your heel on the stool and NEVER apply weights or press on the knee.

hyper extending.jpg

The use of weights or balancing just your heel on a chair or other support are not recommended as they can put too much pressure on tight muscles and ligaments that you want to stretch gently.


As with any exercise, the use of gravity to assist in gaining extension should be done for short periods of time several times a day rather than one big session. The length of time you are in the stretching position should be monitored so that you experience only mild discomfort during the stretch time.

How to "measure" your extension:
  1. Put your leg on a bench, seat, bed, floor or anything similar, but preferably something fairly firm
  2. With not too much pressure, press the back of your knee down - try to engage your leg muscles without pushing hard with your hand
  3. Slide your hand, palm down, under the back of your knee
a) if you can get your entire hand under easily, it's probably about +10 degrees
b) if you can get just your fingers under, it's about +5​
c) if you can get your fingers under but it's a push, it's +0​
d) if you can't get your fingers under at all, it's -5 or more

This image shows the range of motion degrees for a knee joint. Notice that a -10 indicates hyper-extension which you may have had prior to a knee replacement, but it's usually not present after the surgery.

knee ROM small.jpg

Above all, do NOT allow your PT to press on your knee to measure ROM. The only measurement that really counts is what you can do on your own and forcing healing tissue can do more harm than good.
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