Medial tibial stress syndrome is an overuse injury that causes pain along the medial lower third of the tibia bone. It is usually very tender to palpation along the edges of the bone.
There are a number of hypothesis as to what causes medial tibial stress syndrome, but a popular one is the ‘tibial bending hypothesis’. This hypothesis is that it is “bending” of the tibia bone when running is what causes the symptoms. The narrower the base of gait, the more bending there is of the tibial.
When walking we have a base of gait with one foot more beside each other. With running, we tend to put one foot in front of another and have no base of gait. This puts the tibia in a more varus position when running, leading to more bending of the tibial bone. If the volume or intensity of exercise levels increases to rapidly for the body to adapt to those loads, then these bending moments may result in the medial tibial stress syndrome.