The Pelvic Outlet: Anatomy & Movement Support

| Pelvic Joints & Ligaments: Outlet |

The pelvic outlet has two main ligaments that help support the ability of the sacrum to move out of the way to make more room forward/backward in the outlet.

The pelvic outlet has two main ligaments that help support the ability of the sacrum to move out of the way to make more room forward/backward in the outlet.


The pelvic outlet is the bottom opening of the pelvis that creates space for the baby to descend and be born. The outlet’s opening depends on the balance of the pelvic joints and ligaments. We previously demonstrated how an internal rotation of the femur causes the sit bones to move farther apart and increase the side to side opening of the outlet. Let’s discuss how to increase the front to back opening of the outlet by looking at the movement of the sacrum and coccyx (tailbone).

The opening of the pelvic outlet is influenced by the sacrotuberous ligament and sacropinous ligament. Each ligament sort of blends with the other but attach from the pelvis to the sacrum/coccyx. During labor, the sacrum needs to move outwards in order to increase the opening of the pelvic outlet. If these ligaments are “tight,” then the sacrum may not be able to move or may be limited.

If you sit on a tennis ball, you may be able to find these ligaments and massage them out. You can feel for the ligaments by placing your finger in the space between your rectum and sit bones, and then cough. You should feel the ligament tighten. Place the ball there, and then sit down on it and gently massage it out. In points of tension or discomfort, focus a little more there to help release the tension.

The opening of the pelvic outlet is tied to the outward movement of the sacrum. This is why pushing on your back may not be the most beneficial, as the sacrum has nowhere to move out towards, and the opening of the pelvic outlet would be restricted and limited.

Now, how would we open the pelvis from side to side? With internal rotation of the femur!

Internal rotation of the femur opens the ischium, the bottom of the #pelvic opening (the outlet aka where your #baby is trying to vacate the premise from). The posterior portion of the ischium is the Ischial tuberosity, or your sit bones. This is the bony part of the pelvis that you actually sit on. When standing, the glutes cover it but when you sit, they move out of the way.

So how can you accomplish an internal rotation of the femur while in labor? Primarily by having the knees closer together than the ankles; this will generally achieve internal rotation of the femur.
Let’s compare internal rotation versus the typical external rotation (or spreading of the legs) that mothers are told to do during labor…


In this video, I placed white dots on my sit bones (it took a few attempts). When I internally rotate my femurs by keeping my knees together and spreading my ankles apart, you can see that the white dots spread apart from one another. While this opening isn’t massive, it’s still opening! It is an extra bit more space to support the #fetal descent out of the pelvis and into the world!!


internal external rotation peanut ball.JPG

If a mother has an epidural or needs to rest during the final bit of labor, using a peanut ball is a great option to continue to incorporate internal rotation of the femur. Focus on placing the peanut ball between the ankles as opposed to the knees to allow for the internal rotation of the femur to occur!




pelvic outlet movement.jpg

Let’s breakdown some movement that support opening front to back.

When opening the pelvic outlet, we want to think movements that will allow for the sacrum to move out of the way: enter anterior pelvic tilts.

Sometimes during pushing, a mother will naturally begin arch her back in an attempt to move her sacrum and pubic symphysis out of the way of the baby’s descent.

This same arching can be intentional! Insert supported squats or kneeling w an anterior pelvic tilt, so pelvis tilts forward and down (think of making your booty bigger). The anterior tilt of your pelvis allows the outlet of the pelvis to open more from front to back by moving the sacrum out of the way.

Gina Conley