Shorty Swan is excited to share the boney landmarks of your pelvis with you! Often you are called on to organize these landmarks in a Pilates class. Understanding what they are and where they are in a spatial relationship to one another will help you develop stellar form and proprioception, not only in Pilates but in all movements.
Your pelvis is the basin for your organs comprised of four larger bones- your sacrum, coccyx and two hip bones. The pelvis acts as the bridge between the upper body and the lower body. The weight of the upper body is transferred through our pelvis to our legs for motion and all motion in the lower body reverberates up through the pelvis to your spine. How we organize our pelvis greatly affects full body movements.
Hip points/ ASIS
Your hip points are often cued for lining up your pelvis. These boney landmarks are the anterior superior iliac spine or ASIS for short. They are an easily locatable surface on the Iliac crests of your or ridge of your ilia. Looking at the picture below of the front of the pelvis, the wing like bones (labeled 2) are your ilia (plural for ilium), the top edge of each ilium are your iliac crests and the most forward and widest point along the iliac crest is your ASIS.
Your ASIS are cued in Pilates because they are easily felt on the front surface of the body or against the mat. If you place your hands on your natural waist, squeeze in a little bit and run them down your torso you will find your iliac crests. Then use your finger tips to trace the crests around and down towards the front of your body to find your hip points or ASIS. Your ASIS might be where your pants tend to sit and your iliac crest could be what you think of as your hips when actually we can see they are more complicated than that!
Sitz Bones / Ischial Tuberosities
In Pilates we like to know where our sitz bones are all the time. Are they long, tipped up, wide, reaching under? If you sit on a hard surface like a wooden chair or the floor and gently rock from right to left you will feel your sitz bones. It might be helpful to move your glute flesh out of the way a little bit. What we know in the studio as sitz bones are ishchial tuberosities. Tuberosity means a large prominence on a bone which usually serves as a site for muscular attachment. So your sitz bones are tuberosities on the ischium which is the bottom bone of the pelvic bowl (labeled 3). Your ischial tuberosities take the weight of the body when we sit.
Pubic Bone/ Pubis
Your pubic bone is actually two bones called your pubic crests (Labeled 4) that are joined together with a fibrocartilage disc known as the pubic symphysis (labeled 5). While we tend to think of it as one, hard bone It can be helpful to visualize lining up both sides or halves of your pubic "bone" when squaring off your pelvis. The pubic bones are cued so often because, like the ASIS, it is easily locatable on the front surface of the body or against the mat. These surface land marks allow for easier proprioception while you practice as reference points for your boney alignment.
The sacrum (1) contains five fused vertebrae and sits between the two ilia creating the posterior ring of the pelvic girdle. The sacrum is the keystone bridging the vertebral column to pelvic girdle transferring the body weight to the legs. The sacrum and the lumbar spine meet at the junction of L5 and S1. The sacrum meets the top of each ilia at the sacroiliac joints. The sacroiliac joints are broad, flat, synovial joints that were once believe to not move. While SI joints can lose mobility as we age, they remain mobile when healthy. As in any joint, hyper mobility is often problematic. A network of sensory and movement nerves for the lower body run through the sacral plexus, running through the holes in the bone.
Tail Bone / Coccyx
Your tail bone or coccyx is attached at the end of your sacrum at S5 and contains three to five fixed vertebrae. The coccyx serves for muscular attachments, is truly the tail end of your spine and is slightly above and behind your sitz bones.
Related boney landmarks in your femurs (aka thigh bones) are the lesser trochanter and the greater trochanter. More on those when we talk about the hip joint but here is an image for you to run with until then!