I get emailed quite often by people saying that they had been diagnosed with an “anteriorly tilted pelvis” (usually being told that this is the source of their persistent back pain), wanting advice on how yoga can help correct this. This was the inspiration behind this blog post!
Image credit: https://paulgrilley.com/bones
Let’s start by first exploring the basic anatomy of the pelvis. The two hip bones join with the sacrum and the coccyx to form the bowl-shaped pelvis (Latin for ‘basin’). The bones of the pelvis are strongly united to each other to form a largely immobile, weight-bearing structure. The pelvis is the area where the lower limbs attach to the axial skeleton through the sacroiliac joints and therefore plays important roles in movement. The bony pelvis comes together to provide support for the pelvic muscles and connective tissues, which, in turn, provide attachments and support for the pelvic organs.
In the immature skeleton the hip bone is made up of three separate bones: the ilium, the ischium and the pubis. Fusion of these three bones starts to occur around the age of 14 – 16 years and is complete usually by the age of 23 (Moore 1992). The cup-shaped acetabulum, or hip socket, is formed at the area where these three bones meet.
The curved superior margin of the ilium is the iliac crest. You can feel the iliac crest on both sides of the pelvis by placing your hands on your waist and pressing down slightly. The rounded, anterior termination of the iliac crest is the anterior superior iliac spine (ASIS) which can be felt at the anterolateral pelvis. Inferior to the ASIS is a rounded protuberance called the anterior inferior iliac spine (AIIS). Both of these iliac spines serve as attachment points for muscles of the thigh. Posteriorly, the iliac crest curves downward to terminate as the posterior superior iliac spine (PSIS). Muscles and ligaments surround but do not cover this bony landmark and often a depression or dimple can be seen on the skin of this region on the lower back. More inferiorly is the posterior inferior iliac spine (PIIS). Both the PSIS and the PIIS serve as attachment points for the muscles and very strong ligaments that support the SI joint.
The main bony landmarks on the ischium are the ischial tuberosities. They serve as the attachment for the posterior thigh muscles and also carry the weight of the body when we are sitting. They are often referred to as the ‘sitting bones’ or ‘sitz bones’ (from the German verb ‘sitzen’ meaning ‘to sit’).
In terms of tilting the pelvis, I like to think of it as a bowl of water. If we tilt the bowl forward and spill water in front of us, this is anteriorly tilting the pelvis. If we tilt the bowl backwards and spill water behind us, this is posteriorly tilting the pelvis.
No two pelvises are the same shape or size, and no pelvis is symmetrical in any plane. Just take a look at the first image! So, what might look or feel like a ‘neutral’ pelvis for one person will look and feel different for the next person. This makes the concepts of squaring the hip bones or keeping the pelvis level on both sides both challenging and arbitrary. Pelvic tilt is often quantified using the angle between the horizontal and a line connecting the ASIS and the PSIS.
But how can we go about meaningfully defining an anteriorly tilted pelvis if we each have a completely unique pelvis?
In terms of labelling an anteriorly tilted pelvis as the source of someone’s back pain - if only things were that simple! Herrington (2011) studied 120 adults *without* lower back or pelvis symptoms and found that 85% of males and 75% of females presented with an anterior pelvic tilt, 6% of males and 7% of females with a posterior tilt and 9% of males and 18% of females presented as neutral.
Instead of being fixated with the shape of an asana or even with our own standing posture, it is a great idea to spend more time getting to know our unique bodies, exploring both subtle and gross movements and focusing more on the experience of practicing yoga asanas rather than on their form. A wonderful quote by Bernie Clark is:
“Use yoga asanas to get into the body and not the body to get into yoga asanas.”
So, the next time you practice, experiment with the position of your pelvis and see how this affects your experience in each asana.
References:
Herrington, L. 2011. “Assessment of the degree of pelvic tilt within a normal asymptomatic population.” Manual therapy 16(6): 646–648.
Moore, K. (ed). 1992. “Clinically Oriented Anatomy. 3rd ed.” Baltimore: Williams and Wilkins.