Piriformis as an internal rotator?

I’d like to hear from you.  What’s your take on this?

Why is it that we can stretch piriformis by externally rotating the leg as we bring the knee toward the opposite shoulder?  Or in yoga pigeon pose?

Piriformis. The piriformis muscle is a deep muscle located beneath the gluteal (butt) muscles. The piriformis muscle laterally rotates and stabilizes the hip. This muscle is important for athletes who participate in running sports that require sudden changes of direction. The piriformis works along with other hip rotators to turn the hips and upper leg outward (external rotation of the hip). Strong and flexible hip rotators keep hip and knee joints properly aligned during activity and help prevent sudden twisting of the knee during quick side-to-side movements, quick turns, lunges or squats.


Filed under body mechanics, Flagstaff pain relief, hip pain

6 responses to “Piriformis as an internal rotator?

  1. Blake

    When the femur is in anatomical neutral, the piriformis always acts as an external rotator. This is because the origin is on the sacrum, and the insertion is on the greater trochanter of the the femur. The muscle runs posterior/medial/superior to anterior/lateral/inferior, and the angle of pull will draw the greater trochanter posteriorly relative to the femoral head, which results in outward or lateral rotation. When the femur is above ninety degrees flexion, the relationship of origin and insertion is changed: the direction becomes posterior/medial/inferior to anterior/lateral/superior. In this position the angle of pull will cause the greater trochanter to move more medially and superior, and combined with a fixed point of rotation in the socket, will result in inward rotation. That is why when the hip is flexed at greater than 90, outward rotation is such a great stretch of the piriformis. I hope that helps.

  2. gbishop75

    Thanks Blake, this was a bit of a rhetorical question, I do appreciate your feedback however.

    I feel you are about spot on, with the exception of the degrees at which this shift in action occurs.

    “In the neutral hip position the force vectors of piriformis action contribute to hip abduction, extension and lateral (external) rotation. It might be assumed that the hip must flex, adduct and medially rotate to stretch piriformis, but this isn’t the case. As the hip flexes, the rotation moment of piriformis changes such that by full hip flexion it becomes a medial (internal) rotator.” (Travell & Simons, 1992)

    “The transition point for this change in action is considered to occur at about 60 degrees of hip flexion.” (Kapandji 1970, Lee 1989)

    • Blake

      Hi gbishop:

      Thanks for the chance to join in the discussion. I am a little surprised at the generous citing of Kapandji I am seeing on the internet with respect to the piriformis. Although I am sure you are more careful than others, I suspect it is a little like the bible, where everyone quotes it, but no one has read it.
      Kapandji is a venerable name in the pantheon of biomechanical demigods, but even the revised edition of “The physiology of the joints: annotated diagrams of the mechanics of the human joints” only has citations as recent as 1974. Some of the information was derived from cadavers, so that would certainly change the angles (often at an advanced age before death), but even so, there is no indication Kapandji did any primary research.
      Furthermore, Travell and Simmons (who say the role of piriformis changes at maximum flexion, or ~ 150 degrees) and Kapandji (~60 degrees) can not both be correct. If we average the difference, we come up with the modern idea of about 90-110 degrees (Delp, et al. 1999, Dostal et al. 1986, and Neumann, 2010) These measures were obtained with modern radiographic, ultrasound and kinesiological techniques, and in my experience, are more consistent with in vivo clinical assessment and anecdotal evidence. (These also appeared in peer reviewed journals, rather than monographs.) As Neumann points out, this is very easy to prove with a skeleton and a piece of string.
      Anyway, I would much rather be informed than correct, so if you have additional info, I would love it!


  3. Blake

    To be fair, I just found a paper by Pressel and Lengsfeld (1997) using a computer model of the human body that indicates the change from external rotator to internal rotator occurs at 70 degrees of hip flexion. Still, I think the angle of piriformis is more likely to make it an abductor at 70 than an inward rotator unless there is significant neutralization by the adductors (but that’s just a guess).


    • gbishop75

      Thank you for the information Blake! As a therapeutic application I do find that I bring the hip into at least 90 degrees of flexion before considering the use of external rotation for lengthening the piriformis muscle.

      I am not huge on quoting the great biomechanical researchers of our time, or any other time. I do find the information to be of great use in a therapeutic model, an application model, as that’s more of what I do. A therapist. I know a lot of practitioners who want to be the first to share other peoples information with there readers, followers, audience, etc. And that’s great, that is where I learn. The results of research appear to change as we have demonstrated here, it’s nice to have another “angle” on the conversation, thanks again for your input. I apologize if it sounded like I was calling you out to “get it right”…..but after all, now I have another take on this.

  4. Blake

    Hi Geoff:
    I am kind of clueless at times…. I only just figured out that you are a body worker/therapeutic practitioner! I thought at first this was just some general blog. I am both an academic (PhD, Kinesiology) and a body work guy (Thai Massage), so I love seeing practitioners using sound biomechanical principals, and really appreciate your approach to informing your client base and using the ideas in your practice.
    Like you, I also don’t believe in biomechanics or quoting research for its own sake, but sometimes I have a cherished idea about which I am quite mistaken. My discussion here with you has pushed my own thinking at a theoretical level, which will eventually make its way into my hands, and hopefully onto my clients’ hips. So thanks for your open-ness and willingness to play with ideas.



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