Biomechanics · functional reading

Pelvic mobility

Pelvic mobility is the pelvis's ability to change orientation relative to the spine and the femurs: forward or backward (anterior and posterior pelvic tilt), sideways (lateral tilt) and in rotation.

Scientific basis

The pelvis orients itself in all three planes. When moving from standing to sitting, it tilts posteriorly and the sacral slope usually decreases by 20 to 30°; the angle between the pelvis and the femurs closes. These movements are accompanied by movements of the lumbar spine (referred to as lumbopelvic rhythm) and of the hips.

In some people the spine-pelvis unit is stiff, in others very mobile. Reduced pelvic mobility can change how movement and stress are distributed between the pelvis, the spine and the hips.

Blue Portance / SBNFA™ reading

In the SBNFA™ framework, the body regulates and the hips are the regulator: they drive the adjustments, and the pelvis is oriented. Pelvic mobility, particularly in the horizontal plane, and sacroiliac joint mobility contribute to the possibilities for adjustment and stress redistribution, and therefore to positive compensations. In static sitting, the pelvis keeps a balance position of its own; moving away from it requires holding or external support.

Contribution to the analysis of sitting

Seating analysis looks at pelvic orientation, its variations over time and the distribution of support between the two ischial tuberosities. It does not measure radiographic angles.

Not to be confused with

Hip mobility: the hips drive, the pelvis is oriented; pelvic incidence, a fixed morphological parameter that does not vary with posture; pelvic tilt (PT), the angle that measures the orientation of the pelvis; nutation and counternutation, movements of the sacrum relative to the iliac bones.

Sources and scope

Established biomechanical notion. No clinical consequence of a given degree of pelvic mobility is asserted without specific assessment.