Short External Rotator Muscles of Hip

These muscles include piriformis, quadratus femoris, obturator internus, superior gemellus and inferior gemellus.  For their anatomy and functions, please see Lower Extremity Muscle Atlas.  These muscles can be injured by the notorious phase of each running stride - pounding the ground. 

When one stands on one foot, he can lift the contralateral pelvis by one or two inches. This lifting is accomplished mainly by the contraction these muscles. Just like other muscles, they are usually injured when they are used to brake the movement in the opposite direction of the one caused by their contraction.   This movement is the falling of pelvis with upper body on its top when the contralateral foot hits the ground and the femur's downward movement is reversed to upward.  This means the greater the upward acceleration of the leg hitting the ground, the greater braking is needed to stabilize the body by these rotators.  The word acceleration here means in pure physics sense (i.e. it includes the deceleration of the downward movement).

Down hill, hard surface, lack of shoe cushioning and fast pace increases the demanding for these rotators to stabilize the body.  To protect them from injury, one should avoid running on hard surface such as that of concrete as much as possible.  Avoid wearing shoes that do not have or have lost cushioning.  Modern running shoes can last for 500 to 600 miles, but in the last 200 miles or so, the shoes should be worn with cushioning insoles to compensate for the loss of cushioning.  Some shoes, especially those motion control ones, do not have much cushioning to begin with, so they should always be worn with cushioning insoles.  

When these deep muscles are injured,  it takes longer time for them to recover than other shallow muscles.  Deep massage by various means is very helpful.  The better part of their injury is that it allows a good volume of exercise during its recovery as long as the pounding is significantly reduced by slowing down the pace, running on soft surface or wearing shoes with a lot of cushioning.  Even running 70 mpw is acceptable in its later phase of recovery.  Regaining fast pace should be achieved very gradually.

(Originally written in February, 2002)