When walking the range of motion needed at the ankle joint is really important. When we place the foot on the ground the body above needs to move ahead over that foot. This forward motion occurs at the ankle joint, therefore it must be clear that there really should be nothing which prevents that forward movement at that joint. Disorders such as osteoarthritis within the ankle joint can have an effect on that forward motion. Another common problem that might restrict that forward motion are tight calf muscles. They stop the leg moving the necessary range of motion over the foot. If that movement is halted than a number of compensations may occur. Firstly, walking is a lot more difficult. It is more fatiguing as far more effort is required to walk. Secondly, our bodies has got to obtain that movement from somewhere. If it is unable to get that motion at the ankle, then it could get it in the knee and if that occurs we then walk with a more flexed knee which is actually a hard way to walk. If the body does not compensate at the knee, then it gets the motion at the midfoot. In the event that takes place then the arch of the foot flattens which can bring about a range of clinical disorders.
For these reasons, doctors prefer to look at the range of motion at the ankle joint as part of a biomechanical evaluation. There are numerous ways of doing this. One way is a non-weightbearing examination 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 way, is to do what is called a lunge test. This is a weightbearing way of measuring the ankle joint range of motion and in that position it is probably a better representation of the actuality of the way that we move. The lunge test has been shown in research to be reliable and in clinical practice it has been shown to be a very useful tool to use.