There are 33 joints in the human foot. Most of the bones in the foot and ankle have a vertical orientation, meaning they are side by side instead of one on top of the other. This boney arrangement is ideal for dissipating force, which is only possible if the foot is mobile.
The midtarsal joints are designed to unlock and become a moldable adaptor, and then lock to become a fixed propeller during ground-based movement, especially gait. Failure to have this midtarsal joint motion increases injury risk at the knee and low back.