What causes shin splints?

1. Muscle imbalances between anterior tibialis and calve muscles (soleus and gastrocnemius)- tight calves and a weak anterior tibialis.
2. Flat feet - causes the anterior tibialis to become overstretched, weakened and inflamed.

Shin splints are caused by a foot strike strategy that emphasizes anterior tibialis recruitment in favor of the posterior leg muscles. This could happen for a few reasons:

1. Habitual heel-strike walking pattern as opposed to a more mid-foot strike pattern,

2. Your walking/running pattern doesn't match the shape of your femurs (anteversion or retroversion). This increases muscle recruitment and therefore stress to the leg, or

3. Under-recruitment of  your gluteal muscles to assist in advancing your leg while walking or running.

There are actually two kinds of shin splints, anterior and posterior shin splints.

Anterior shin splints are the most common and tend to affect people who take up a new activity, such as jogging, sprinting, or playing sports that require quick starts and stops. The unfamiliar forces place a heavy strain on the anterior tibialis, a  muscle located on the front side of the lower leg.  Unfamiliar forces or stress can cause this muscle to become irritated and inflamed. This commonly happens when people who are not regular runners decide to go on a long jog. The anterior tibialis muscle must work hard to control the landing of the forefoot with each stride. Running downhill can place even more demand on this muscle in order to keep the forefoot from slapping down on to the ground. People who run on the balls of their feet or who run in shoes with poor shock absorption can aloso be more succeptible to anterior shin splints. To avoid anterior shin splints, individuals should ease into any new activity and slowly progress their activity.

Posterior shin splints are generally caused by imbalances in the leg and foot. Muscle imbalances from tight calf muscles can cause this condition. Imbalances in foot alignment, such as having flat feet (lack of arch in the foot), can also cause posterior shin splints. As the foot flattens out with each step, the posterior tibialis muscle becomes stretched, causing it to repeatedly tug on its attachment to the tibia. The attachment of posterior tibialis eventually becomes damaged, leading to pain and inflammation along the inside edge of the lower leg.  To avoid posterior shin splints, individuals should engage in a corrective exercise program that addresses the individual's muscle imbalances and teaches proper movement patterns.

• Worn out sneakers can cause shin splints because of their lack of support of the arch of the foot.
• Running on hard surfaces such as pavement or outdoor/indoor tracks cause repeated trauma to the lower leg, which can cause shin splints.
• When beginning a new exercise program, doing too much too soon can cause shin splints, as the muscles have not had time to acclimate to the increased demand.
• Having flat feet causes the foot to roll inward during each step, which can cause pain along the front lower leg.
• Running downhill causes the muscles to lengthen during exercise rather than shorten, which causes more trauma to those muscles than they normally would receive.

(This answer provided for NATA by the Eastern University Athletic Training Education Program.)