When walking the range of movement needed at the ankle joint is really important. When we place the foot on the floor the body above is required to move ahead over that foot. This forward movement occurs at the ankle joint, therefore it should be obvious that there really should be nothing that prevents that forward motion at that joint. Disorders such as arthritis within the ankle joint will impact that forward movement. Another common problem which can restrict that forward motion are tight calf muscles. They stop the leg moving the desired range of motion above the foot. In the event that movement is restricted than a number of things can occur. Firstly, walking will be a lot more difficult. It is more fatiguing as far more efforts are required to walk. Secondly, our bodies has to get that movement from somewhere. If it is unable to get that movement at the ankle, then it could possibly get it at the knee and when that takes place we then walk with a more flexed knee that is a hard way to walk. If the body does not compensate at the knee, then it gets the motion at the midfoot. If that takes place then the arch of the foot collapses which can lead to a variety of clinical conditions.
For these reasons, doctors want to measure the flexibility at the ankle joint as part of a biomechanical evaluation. There are several ways of 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 approach, would be to do what is known as 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 walk.