Medial = tibialis posterior
Anterior = tibialis anterior
What is it?
Medial shin splints are a condition wherein the periosteum of the tibia is damaged when it is pulled away by an overstressed tibialis posterior muscle.
Anterior shin splints are a condition wherein the blood flow is obstructed from the anterior compartment due to the hypertrophy of the overstressed tibialis anterior compartment.
What are the common symptoms/complaints?
Medial shin splints: Patients complain of a dull, aching pain felt along the medial side of the tibia. Once it starts, any activity will aggravate it.
Anterior shin splints: Patients complain of dull, aching pain felt along the anterior side of the tibia. This can be a medical emergency due to lack of blood flow leading to neurosis and gangrene of muscle in the anterior compartment.
How is it caused?
Medial shin splints: The tibialis posterior muscle plantarflexes and inverts the foot (anti-pronator) due to its distal attachment (insertion) on the medial aspect of the foot. During over-pronation the tendon of the tibialis posterior is stretched and pulled upon excessively, thereby attacking the weakest area, namely its origin (proximal attachment) on the periosteum of the tibia. The small pain fibres of the periosteum are torn away, causing pain and chronic inflammation.
Anterior shin splints: The tibialis anterior muscle dorsiflexes and inverts the foot, acting as an antipronator due to its distal attachment (insertion) on the medial aspect and base of the first metatarsal. During over-pronation the tibialis anterior muscle fibres must fire constantly to oppose (re-supinate) the over-pronation, thus causing hypertrophy (swelling) of the tibialis anterior compartment. With the anterior compartment being tightly constricted, the swollen tibialis anterior can cause an obstruction of blood flow, which, in turn can cause severe pain due to ischemia (lack of oxygen). This can be very serious, and may require emergency surgery. An example of Ischemia is angina.
How is it treated?
Medial and anterior shin splints: Depending on the severity of the injury, treatment may include standard acute care, restricted activity and an orthotic device that corrects the over-pronation and stops the foot from falling too far medially (reducing the strain on the tibialis posterior) and facilitates proper foot function and timing, reducing the stress on the tibialis anterior.