Commonly overlooked is the Interosseous Membrane (IM), which is a broad, thin tissue that separates the tibia and fibula bone in the lower leg. The characteristics of the IM are similar to that of a thick ligament- it provides stability but it also helps to bear and distribute load via its fibres.
Within the IM are different types of nerves that are responsible for sensing pain and mechanical forces such as:
• Joint position
If there is an abnormal change in the tissue these nerves will respond, possibly causing:
A common way for abnormal change to occur in the tissue is when the muscles attaching to the IM are not functioning correctly.
The muscle that has the largest attachment onto the surface of the IM and hence the largest influence on the nerves is the tibialis posterior muscle. This muscle originates on the IM but inserts onto a bone in the foot called the navicular.
It is also the primary muscle that supports the arch of the foot. Ideally, when you walk the tibialis posterior muscle lifts the navicular bone and inner arch up and then releases it to allow the arch to drop- this enables the proverbial spring in your step!
However, if the navicular bone is not moving correctly it ‘pulls’ on the tibialis posterior muscle which then ‘pulls’ on the IM, consequently firing off these nerves, causing pain in your shin!
This is a common finding in those patients who suffer from shin splints.