Anterior vs. Posterior Pelvic Tilt
Anterior and posterior pelvic tilts are a necessary component of proper lumbopelvic mechanics. As the body moves into a posterior tilt, the lumbar spine flexes and there is a loss of lordosis. During an anterior tilt, the lumbar spine extends and the natural lordotic curve increases. Individuals with sacroiliac joint pain or low back pain often lose the ability to perform these movements. One movement is not superior to the other, but rather it is more important to be able to control the transition from an anterior to posterior tilt.
BackGround INformation: The Lumbar Spine to Sacroiliac Joint Connection
Many people become confused when assessing the lumbosacral region. For some clinicians, it is often hard to decipher if pain is arising from the low back, SI Joint, or a combination of both (See my post on TSPT to learn more about this!)
For this reason, it is important to simplify the lumbopelvic exam. When assessing the pelvis, remember there are only:
- 3 bones (2 innominates, 1 sacrum)
- 3 joints (left and right sacroiliac joints, pubic symphysis).
- >35 muscles that attach to the pelvis, but these can be separated into groups (adductors, extensors, rotators, etc...)
Motion in the lumbopelvic region can either be Iliosacral (ilium moving on the sacrum) OR sacroilial (sacrum moving on the ilium).
Ilio-sacral movement is the ilium moving relative to a fixed sacrum. It may help to think of the ilium as a continuation of the femurs.
Sacro-ilial movement is the sacrum moving relative to ilium. It may help to think of the sacrum as a continuation of spine.
Since these movements are not well defined in the literature, do not focus too heavily on one versus the other. More importantly, the clinician needs to identify the restricted and painful movement patterns.
Anterior & Posterior Tilt during a functional movement
In the left picture, the person maintains an anterior pelvic tilt as she moves into the hamstring stretch. The relative anterior tilt increases the tension on the hamstring muscles, which significantly increasing the stretch. Additionally, the anterior tilt places a natural opposing stress across the SI ligaments. As she bends forward with an anterior tilt, the sacrum follows the spine and attempts to maintain lordosis. Contrarily, the ilium is pulled into a posterior tilt from the hamstring muscles. If stiffness in the hips or low back exists, this motion will be difficult to perform.
While this position is uncomfortable for many people, maintaining a neutral spine (or slight anterior tilt) is generally recommended when stretching the hamstrings or bending forward.
In the right picture, the person rests in a posterior tilt as she moves into the hamstring stretch. The posterior tilt decreases the tension on the hamstring muscles. To successfully reach forward from this position, excessive motion must occur from the thoracic and lumbar spines. As she bends forward with a posterior tilt, the sacrum and ilium are free to move in the same direction. From a biomechanics perspective, the sacrum is 'unlocked' in this position. The lumbar flexion may place excessive amounts of stress across the lumbar spine. This same compensation may occurs when assessing hip flexion in supine.
Read about Hip Flexion vs. Lumbar Flexion.
While this position is more comfortable for many people, the posterior tilt and flexion of the lumbar spine is usually not indicated while trying to stretch the hamstrings or bend forward.
In the comparison pictures above, many individuals attempt to stretch their hamstrings from a posterior pelvic tilt. This position feels natural since most of our society are more comfortable in a position of flexion of the lumbar spine. Unfortunately, repetitively moving from the lumbar spine into flexion usually becomes painful if the spine is not prepared for the movement. As I mentioned at the beginning of the post, both movements are equally important! Teaching clients how to move their pelvis will help unlock both hip and lumbar mobility deficits. Personally, I often use the Cat/Cow Exercise to initiate these pelvic movements. It is most important that clients understand when and how to control each movement during various daily activities.