The piriformis is an external rotator of the hip that attaches proximally to the anterior surface of the sacrum and
inserts onto the superior aspect of the greater trochanter. The near horizontal alignment of the muscle which is primary rotator. Also, the insertion at the top of the greatnction of the piriformis. Certainly, it is an external rotator and hip abductor in the anatomic position of 0⁰ of hip extension; 0⁰ of hip flexion; 0⁰ of adduction; 0⁰ of abduction; 0⁰ of internal rotation and 0⁰ of external rotation .
However, the researchers said ,neutral is very rare in the real world. As the hip moves, the function of the hip muscles change. When the hip is at about 45⁰ of flexion (see the image), the line of pull of the piriformis now makes it act as a purely coronal plane muscle (abduction) with little to no transverse plane influence .
As the squat depth increases(see right side image), the line of pull of the piriformis continues to change. Past 90⁰ the piriformis becomes an internal rotator of the hip . the function of the piriformis, is consider the position of the knees during the overhead squat assessment.
When the knees demonstrating valgus during a squat assessment indicates that the piriformis isn’t holding up the femur in alignment. Since the muscle acts as an abductor at these angles, if the knees are adducting then the muscle is lengthening.
Remember the more they are pulled, the tighter they get. Therefore, if a patient knees demonstrate the valgus position, the piriformis does NOT need to be stretched. However, if a client demonstrates knee varus , then the piriformis may be short and stretching may required.
let us consider the muscles opposite the piriformis. While there may be several, a key muscle group is the adductors. Thus, the client with knee valgus may have short and overactive adductors that internally rotate which pull the femur and subsequently pull on the piriformis.
Remember it is only a primary external rotator at neutral, and then, as the hip begins to flex, it serves more of an abduction role,until greater than 90°, then becomes an internal rotator. Thus, to perform a great piriformis stretch, the hip needs to be flexed to about a 45-65⁰ degree angle and adducted
I frequently have friends who perform the stretch which we describe above and quickly hear from patient that they don’t feel any stretch. Do not scratch your head because they DON’T need to stretch it. The muscle is likely long, not short.
Lets see, What is Piriformis Syndrome and what can we do about it?
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