Are you sitting comfortably..? Understanding the role of the pelvis in achieving a stable posture
The pelvis is the big, bowl-like structure that sits in the middle of the body. The top of the pelvis can be felt just below the waist.
The back of the pelvis joins onto a triangular bone (called the sacrum) that sits at the base of the spine. The spine and the pelvis join at the sacrum and therefore the position of the pelvis will change the position of the spine.
At the front, the pelvic bones join to form the pubic bone. The leg bones (femurs) join on to the pelvis at the hip joints and you sit on two bony prominences that are part of the pelvis (you can feel them if you slide your hand under your buttock when you are sitting).
Because the pelvis supports the spine, provides the 'sitting bones' and is joined to the thigh bones, it is like a keystone. This means that if the pelvis is in a good position, the rest of the body tends to follow.
Movements of the pelvis
The pelvis can move in three different ways:
As each movement is explained, notice how the position of the body changes when the pelvis is moved.
The pelvis can tilt forwards making the small of your back more hollow
The pelvis can be in a neutral position when you are sitting up straight
The pelvis can tilt backwards causing the spine to adopt a C-shape
The pelvis can rotate so that one hip is further forwards than the other.
The pelvis of someone sitting in a wheelchair with the pelvis rotated so that the right hip is further forwards than the left hip. This would make the right knee further forward than the left knee.
One side of the pelvis can lift up so it is higher than the other. In this position weight is usually resting more on one of the sitting bones.
Spine curves sideways to compensate. Left side of the pelvis is higher than the right. Extra weight on the right sitting bone.
Problems with posture in sitting are often caused because the pelvis has fallen out of the neutral position. Having the pelvis in the wrong position can then lead to problems in the legs and also the spine which in turn will affect the position of the head.
People with MS commonly sit with their pelvis tilted backwards and with their spine in a C-shape. This may cause back pain or neck pain as often the curve in the neck has to be increased so that the person can look forwards.
Use P.E.A.K. as a quick reminder of how to check your position each day:
P - pelvis in a neutral position
E - equal weight on both buttocks
A - 90° angles at hips, knees and ankles
K - knees facing forwards
The following pages will go through the steps you need to follow to improve your sitting posture.