The Pelvis

Located in the lower torso, the pelvis is a strong group of bones that protects the delicate organs of this pelvic area and also has powerful muscles of the hip, thigh, and abdomen attached.

Anatomy

The pelvis doesn’t fully fuse together until puberty.
The hip flexors attach both onto and across the pelvis.
At the back of the pelvis is the sacrum (the body’s centre of gravity). It creates a strong foundation for the spine.
The legs dangle from the pelvis.

Bones of the pelvis:

Ilium (ilia/ilio/iliac) – large flat area of the pelvis
Ischium (ischia / ischio / ischial) – rear end of the pelvis (sit bones). The hamstrings attach here.
Pubic Bone (Pubo / pubis) – located at the front by the pubic area of the body.

The three bones merge in the centre of the pelvis (at the acetabulum). The ball of the femur also attaches here. This socket (acetabulum) creates the hip joint.

The two sides of the pelvis are attached by cartilage (pubic symphysis) and at the back by the sacrum. The sacrum meets the ilium and the sacroiliac joint.

The Sacroiliac (SI) Joint

This is the joint between the sacrum and the ilium bones of the pelvis, which are connected by strong ligaments. The sacrum supports the spine and is supported in turn by an ilium on each side.

Most people have little movement as the ligaments are thick and dense.

Movement of this joint is created by the tilt of the pelvis.

Muscles attached to the pelvis:

Hamstrings
The erectors of the spine
Abdominals
Quadriceps
Adductors
Iliopsoas
Pelvic floor muscles (Perineal) – acts as a diaphragm. When these engage, they help lift of tighten the anus, which stabilises the spine.
Transverse perinei
Bulbospongiousus
ischiocavernosus

Male v Female Pelvis

The shape of the female pelvis is wider to allow them to carry a baby.

Movement

If the pelvis moves, it impacts the hip joint, sacrum and lumbar spine.

The legs come down from the pelvis and the feet are indirectly supporting the pelvis.

Anterior tilt

Pubic bone moves down, lumbar curve is accentuated
Muscles that attach the front of the pelvis create this action (adductors, quadriceps, and psoas).
These muscles work in conjunction with the muscles that attach to the back of the pelvis

2. Posterior tilt

Pubic bone lifts, lumbar curve in the lower back flattens.
The muscles at the front and above the pubic bone lift the pelvis (abdominals work in conjunction with the hamstrings.

3. Lateral tilt

Lifting one hip upwards
The spine bends to the side (lateral flexion)

4. Pelvic rotation

This can be seen when standing when the pelvis rotates forward.

Yoga Implications:

The position of the feet impacts the position of the pelvis.
Reducing a posterior tilt – bending the knees in downward dog can help the pelvis sit neutrally if the hamstrings are tight.
Increasing a posterior tilt – if we engage the abdominals, we can tilt the pelvis to bring the spine more flat. e.g. reclined hero pose (supta virasana).
SI joint – If tight hamstrings in forward folds, this can cause a posterior tilt to the pelvis which will put force on the SI joint. Bending the knees can reduce some of this tension.
Backbends – causes an anterior tile in the pelvis. Be careful not cause too much strain on the SI joint by bringing the pelvis more towards a posterior tilt.
Twists – be careful not to go too deep around the SI joint. You could do more of the twist at the hip joint to not over stretch the lumbar spine if you have problems with the SI joint.
Mula Bandha (root lock) – Pelvic floor muscles engage which also causes the abdominals to contract. The pelvic floor muscles are also at the base of the spine.