Pelvic girdle pain and relevance of ASLR testing: A ... - Cindy Verheul

The function of the pelvis is now to transfer the “load”. (DonTIGNY 1985; A Vleeming 2007;
Jan Mens 2009)
2.1.3 Mobility of the pelvis
Counternutation nutation are the movements which may occur in the SI joint. Nutation is a
relative rotation of the anterior sacrum to the iliac bones. The mobility here is at the end of
pregnancy at its maximum.
At asymmetrical movement of the pelvis there is an opposite movement in both SI joints but
also a movement in the pubic symphysis. In the pubic symphysis a so called “vertical shear”
will take place. This mobility is normally within the limits of the joint.
The stabilizing mechanisms of the pelvis
There are three mechanisms to give the pelvis its stability:
1. The form closure by the shape of the articular surfaces of the joint.
2. The force closure
3. Self-locking mechanism.
The form-closure is a passive mechanism the others are total or partial activation
mechanisms. Below, these mechanisms are described and elucidated. (A. L. Pool-
Goudzwaard et al. 1998; A Vleeming 2007)
- Form closure:
This is a term for the stable situation with closely fitting joint surfaces, where no extra forces
are needed to maintain the state of the system, given the actual load situation. (A. L. Pool-
Goudzwaard et al. 1998)
There are three reasons why there is a stability in this form in the SI joints. (A. L. Pool-
Goudzwaard et al. 1998; A Vleeming 2007)
The first reasons is due to the wedge-shape from the sacrum. That is stabilized between the
two iliac bones through this form.
Secondary the roughened articular cartilage which is in contrast with a normal synovial joint.
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