When walking the range of movement available at the ankle joint is really important. Whenever we put the foot on the ground your body above needs to move forward over that foot. This forward movement takes place at the ankle joint, so it should be clear that there really should be nothing which prevents that forward movement at that joint. Problems such as osteoarthritis in the ankle joint can impact that forward movement. Another frequent problem that could restrict that forward movement are tight calf muscles. They stop the leg moving the required range of motion over the foot. If that motion is stopped than a number of things can occur. Firstly, walking is quite a bit harder. It is more fatiguing as more effort is needed to walk. Secondly, your body has to get that motion from someplace. When it can not get that motion at the ankle, then it may get it in the knee and if that happens we then walk with a more flexed knee that is a difficult way to walk. If the body doesn't compensate at the knee, then it gets the movement at the midfoot. If that takes place then the arch of the foot collapses which can bring about a range of clinical problems.
For these reasons, clinicians prefer to look at the range of flexibility at the ankle joint as part of a biomechanical evaluation. There are many methods for doing this. One of the ways is a non-weightbearing test with the foot and leg up in the air and the foot is just moved on the leg and the range of motion is assessed. Another, perhaps better method, is to do what is known as a lunge test. This is a weightbearing measure of the ankle joint flexibility and in that position it is usually a better representation of the actuality of the way that we move.