SI and Lumbar Facet Pain
By Stan Andrzejewski • January 15th, 2006 • 17618 Views
The following article is an in-depth analysis (anatomy and mechanical function), of the pelvis and lower verterbral structures. To assist your reading, understanding, and application of the following information, you may want to refer to a detailed anatomy text.
Anatomy of the Pelvis
The pelvic girdle is comprised of 3 bones: 2 ilia and a sacrum. The front of the pelvis is the pubis, a joint where the 2 ilia meet. The ischial tuberosities are what we sit on [sit bones]. The anterior /posterior superior iliac crests [ASIS / PSIS] are the hipbones. Sacroilial joints connect the sacrum to the ilia.
The male pelvis has more massive bones than the female pelvis. There is an 80 mm outlet. The sacrum is more triangular; therefore, more wedging, more locking. The ilia articulate the sacrum at S 1,2,3,4. The male pelvis is a more stable pelvis.
The female pelvis has thinner bones. It has a larger, 120mm, more circular outlet for a birth canal. The female pelvis has their acetabulum [hip sockets] set wider. The sacrum is more rectangular. SI articulation surface are only at S 1,2,3. These joint surfaces are shallower. A hormone, relaxin, during menstruation and pregnancy, especially last 3 months create a less stable pelvis by loosening the ligaments. This of course is necessary for mobility of the S/I joints during childbirth. But unfortunately this mobility allows for more SI dysfunction. As well childbirth strain, intercourse strain, baby on hip strain can contribute to more S/I mechanical stress.
The ligaments of the pelvis are many. The intrinsic ligaments tie pelvis together. They include the anterior sacroilial ligament, the short and long posterior sacroilial [stretched by anterior ilial rotation].
The extrinsic ligaments hold pelvis together. They include the sacrotuberous ligament [stretched by posterior ilial rotation]. This ligament ties into the biceps femoris [outer hamstring]. This ligament stretched with forward bends is an extension of the hamstrings. Also included is the iliolumbar ligament that attaches from the transverse process [TP] of L4, 5 to the ilium.
There are 35 muscles attached to pelvic girdle. The pelvic floor is basically the levator ani muscles, which are sling like in shape, maintaining low-level contraction, or postural support of internal organs of bladder, uterus, and bowel. They attach to the obturator tendon, pubis, sacrum, and inner surface of ilia. ...