Sacrum

Well, just to get started. The “sacrum” is the sacred bone. This is the section offered to the gods when animals were “sacrificed”. In Italian families the part of the animal “that goes over the fence last” is also called the “best part” so that the youngsters won’t spit it out when this nasty bit is plopped on their plate. Why this part was an offering is suspect. There is probably some historian out there to whom this makes sense.

Strange name aside, the sacrum is the section of the spine that completes the pelvic ring. Imagine if ribs were much wider, and then all stuck together (unseparated). Well, that is what the pelvis is, in essence.

The sacrum is five vertebrae which did not separate as moving entities from each other. They have no disc or small joints articulating, just one big hunk. The transverse processes are also in one blob per side as the “ala” (singular) or alae (plural).

The sacral ala is what actuall y contacts the pelvic bone called the ilium. The ilium is the “hips” when you “put your hands on your hips” which isn’t hip joint. Above you can see the hip joint, the obvious ball and socket joint. The hip “bone” is - who knows what? Just about anything gets called that. But the big pelvic bone is the ilium.

Now just stand back and look at the arrangement. The pelvis, including the sacrum, is a ring that is balanced like a seesaw on the two hips. In front, abdominal muscles span the chest and sternum to the front of the ring. If the abdominal muscles are weak, or lax, then the front of the pelvis goes down. Snug those abdominal muscles and the front of the pelvis lifts.

Lifting the pelvis from the front lowers the sacrum and makes it more vertical. That reduces lumbar lordosis. Abdominal muscles control lumbar lordosis. See? But hip flexion contracture pulls the front of the pelvis down. That makes more lordosis.

The articulation between the sacrum and the pelvis - the sacroiliac joint - does not have much movement. It does give a bit, and allow some forgiveness to the ring structure, but overall it is a firm continuation of the hoop.

Coccyx

The purpose of the coccyx is to hurt when we land on it. It completes our union with the animal kingdom. Were it longer it would spare us in our misadventures on monkey bars, but alas - no - perhaps pay back for offering the wrong part as sacrifice. It is named after the Cuckoo’s beak. Does THAT make you feel better?