When walking the range of motion available at the ankle joint is really important. Whenever we place the foot on the ground your body above needs to move forward over that foot. That forward motion comes about at the ankle joint, so it ought to be evident that there ought to be nothing which stops that forward motion at the ankle. Problems such as osteoarthritis in the ankle joint can have an effect on that forward movement. Another frequent problem which may obstruct that forward movement are tight calf muscles. They stop the leg moving the necessary range of motion over the foot. If that movement is stopped than a number of compensations can happen. Firstly, walking is quite a bit harder. It is more tireing as much more efforts are required to walk. Secondly, your body has to obtain that movement from someplace. If it is unable to get that motion at the ankle, then it could get it in the knee and if that happens we then walk with a more flexed knee which is actually a difficult way to walk. If the body doesn't compensate at the knee, then it gets the motion at the midfoot. In the event that takes place then the arch of the foot collapses which can result in a variety of clinical conditions.
For these reasons, clinicians prefer to look at the range of motion at the ankle joint as part of a biomechanical assessment. There are numerous methods for doing this. One of the ways is a non-weightbearing examination with the foot and leg up in the air and the foot is just moved on the lower limb and the range of motion is assessed. Another, probably better method, would be to do what is known as a lunge test. This is a weightbearing way of measuring the ankle joint flexibility and in that position it is usually a better representation of the actuality of the way that we walk.