Peroneals-Posterior Tibialis Interaction

Imagine a classic tug of war…

As one team pulls hard on the rope, the other team gives a little and stretches out their arms as the flag in the middle moves closer to the team which is pulling harder.  Then, the team with outstretched arms regains their composure and pulls the flag back towards them.  The flag will move back and forth, back and forth until finally one team is overpowered and loses.

Collectively, the Peroneals and Posterior Tibialis work just like a classic tug of war with the foot acting as the flag.  As we have discussed, muscle shortens as it contracts.  So, as the Peroneals contract and shorten, the foot will evert and move the foot outwards.  Likewise, as the Posterior Tibialis contracts and shortens, the foot will invert and move the foot inwards.

A struggle of powers is born…

If one of the muscles is tight, due to poor flexibility or a spasm, the other muscle group is going to be put on stretch and eventually tissue breakdown will occur.  Likewise, if one of the muscles is significantly stronger than the other, it will over power and cause tissue damage.

What occurs more often than a tight or weak muscle, is a biomechanical issue which puts a strain on one or the other.  Most often, this is due to a leg length inequality.

Leg Length Inequality Shows Up Again

When a leg is short, oftentimes the body will try to lengthen it by actively inverting the foot by firing the Posterior Tibialis muscle.  This can cause problems in either muscle.  Some people will have issues in a Posterior Tibialis which is not strong enough for the increased load.  Others will have trouble with their Peroneals as they are placed in a stretched position with every step.

When a leg is long, many times the body will attempt to shorten it by actively everting the foot (pronating) to shorten it.  Similar problems occur as the first scenario.  The Posterior Tibialis may become inflamed due the constant stretch, while the Peroneals can become injured due to an overloaded muscle.

So, what’s the lesson here?  If an athlete has pain in one of these muscles, don’t just look at the point of pain.  Make sure you address, the foot, ankle, Pelvis and everywhere in between.