When walking the range of motion available at the ankle joint is so important. Once we put the foot on the ground the body above is required to move ahead over that foot. This forward movement takes place at the ankle joint, so it should be evident that there ought to be nothing which prevents that forward motion at the ankle. Disorders such as arthritis in the ankle joint may affect that forward movement. Another common problem which may restrict that forward movement are tight calf muscles. They stop the leg moving the required range of motion above the foot. If that motion is stopped than a number of compensations can occur. Firstly, walking is a lot harder. It is more fatiguing as more effort is required to walk. Secondly, your body has to get that movement from somewhere. If it can not get that motion at the ankle, then it could possibly get it at the knee and if that occurs we then walk with a more flexed knee that is a difficult way to walk. If the body does not compensate at the knee, then it gets the motion at the midfoot. In the event that occurs then the arch of the foot collapses and that can cause a range of clinical disorders.
For these reasons, doctors prefer to measure the flexibility at the ankle joint as part of a biomechanical evaluation. There are numerous ways of doing this. One way is a non-weightbearing test with the foot and leg up in the air and the feet are just moved on the leg and the range of motion is tested. Another, probably better method, is 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 move.