This is something that has troubled me for a long time.
Traditionally we have considered the normal range of ankle dorsiflexion to be 10 degrees with the subtalar joint held in its neutral position (as subtalar joint pronation allows for more dorsiflexion and is not really the ankle joint).
- A number of things troubled me with this concept of 10 degrees:
- Where did it come from? A review of the literature cannot find a basis for it with most studies looking at the ankle joint range of motion reporting a different value.
- What if you walk faster, do you need more? What if you walk slower, do you need less? If this was the case, does this not make a mockery of the normal of 10 degrees.
- The textbook definition is to dorsiflex the foot to resistance and measure that angle. What is ‘resistance’? How hard should you push? Can I get 10 degrees in everyone if I push hard enough? Theoretically, when testing ankle joint dorsiflexion, we should be dorsiflexing the foot on the leg with the same magnitude of forces that are applied during gait. Are we physically capable of pushing that hard?
- Even if we accept 10 degrees as normal, then everyone wears shoes with at least a 1cm heal raise, which decreases the dorsiflexion demands on the ankle joint!
- My honours students a few years ago (Lisa) looked at how far the tibia moved over the foot before the heel came of the ground at different speeds. Everyone was different. Some subjects may have had 15 degrees on measurement, but the heel came of the ground when the tibia got to a few degrees. Some people needed less when they walked faster (they just lifted the heel off the ground sooner). Some people need more when they walked faster. Some had a limitation when measured clinically, but had and needed > 10 degrees when walking. There was no consistent pattern and everyone was different.
Life used to be simple. If they had less than 10 degrees, then we used a heel raise and got them to stretch. If they had more than 10 degrees, then there was no intervention. It was that simple.
What is the normal range of motion for the ankle joint? I have no idea! It is obviously subject specific.