How Your Pelvis Moves on Your Leg

In this video I explain how the left side of your pelvis moves on top of the left femur.

Why should you care about such a seemingly inconsequential piece of esoteric information?

Because it’s not inconsequential at all!!!

It could be the most important joint movement out of all the movements in the human body.

I say this because it is the first movement we lose as we develop a Left AIC pattern and being to favor the right side of our body (regardless of handedness).

So many compensations that occur, things like altered breathing patterns, SI joint dysfunction, lack of shoulder range of motion, certain types of Tempo-mandibular joint dysfunction and even foot issue like plantar fasciitis, could all potentially have their origin in the inability of your left ilium (one bone that makes up the four-boned pelvis) to move properly on top of your left femur.

Quick anatomy: The femur inserts into the pelvis at the acetabulum. The femur/acetabulum intersection is the hip joint.

However, uniquely to Postural Restoration Institute, we take it a step further, identifying the joint by what bone is moving on what bone.

An acetabulum moving on a femur is called AF (or A on F). The acetabulum’s movement on the femur is classified as either

  • AF/IR- acetabulum/femoral internal rotation. Acetabulum moving internally on the femur.
  • AF/ER- acetabulum/femoral external rotation. Acetabulum moving externally on the femur.

Normal human walking requires that we can AF/IR and AF/ER in an alternating fashion.

The ubiquitous Left AIC pattern consists of a left ilium (acetabulum) that is stuck in AF/ER on the femur. As you walk and run and do whatever it is you need to do, the left ilium never achieves, or never fully achieves AF/IR.

Importantly, these alternating movements, AF/ER and AF/IR have to occur to move without compensation.

If these alternating movements don’t occur, compensations will inevitably occur and eventually these compensations can build up until the brain says “enough” and gives you pain.

Pelvic repositioning is designed to get the left ilium, the left side of the pelvis, the left acetabulum, out of AF/ER and train it to achieve AF/IR so that you can eliminate potentially compensatory movements.

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