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Examining the Anterior Pelvic Tilt

We are all aware that posture or body position plays an important, if not crucial, role in the healthy function of our musculoskeletal system. Some types of compromised or dysfunctional posture are easy to evaluate.

Elevated shoulders or forward head posture, for example, are frequently cited as key components of upper back, neck and headache pain.

Pelvic alignment is frequently noted as a key factor in many soft-tissue disorders as well. Yet determining ideal pelvic alignment is challenging and there is often misinformation about what actually produces pelvic misalignment. Let's take a closer look at specific biomechanical characteristics of pelvic alignment and their importance in constructing an appropriate treatment plan.

 Pelvic Tilts Defined

The most common pelvic misalignments are referred to as pelvic tilts. There are three types of pelvic tilt: anterior, posterior and lateral. This article takes a detailed look at the anterior pelvic tilt, and explores key principles of how they develop, common misunderstandings and treatment considerations.

Axis of rotation. Let’s clarify some anatomical and biomechanical principles first. The pelvis is composed of two halves which join anteriorly at the pubic symphysis and posteriorly at the sacroiliac joint on each side. Each half of the pelvis is also referred to as an innominate bone (consisting of ilium, ischium and pubis). Each innominate moves independently of the other, although most frequently we see pelvic misalignments involving the two innominates moving together. For our purposes in this article, assume that both innominates are moving together.

Each of the pelvic tilts involve rotary motion whereby one bone is rotating around an axis point of another. A simple analogy is a pinwheel which rotates around a point at the center of the pinwheel. The point at the center of the pinwheel is called the axis of rotation (Figure 1). It is crucial to understand the anatomical axis of rotation for pelvic tilts, because this is one of the key factors that leads to common misunderstandings about how a pelvic tilt functions biomechanically.

In an anterior tilt, the pelvis tips downward in an anterior direction so the pubic symphysis moves inferiorly. A common misconception about the anterior pelvic tilt is that the axis of rotation is at the sacroiliac joint. There is only a minor degree of movement capable at the sacroiliac joint and not enough to provide significant rotary motion. The actual axis of rotation for anterior pelvic tilt is at the iliofemoral (hip) joint.

An anterior pelvic tilt is most commonly caused by the combined actions of muscles on opposite sides of the body which act together to create the dysfunction. Tightness in the iliopsoas and rectus femoris (hip flexor) muscles combined with tightness in the erector spinae, multifidus and quadratus lumborum (back extensor) muscles produce the anterior tilt. These muscles act like a force couple to produce the anterior rotation 

The anterior pelvic tilt simultaneously creates an exaggerated lumbar lordosis. Many individuals with this postural distortion are told they have weak abdominal muscles and need to focus on strengthening exercises to offset the postural distortion. However, if the underlying muscular dysfunction of the hip flexors and low back extensors is not addressed, strengthening exercises of the abdominal muscles will have little benefit.

There are other detrimental effects that result from the anterior pelvic tilt. When the lumbar lordosis is increased, there are greater compressive loads on the posterior vertebral arch structures. The increasing compressive loads on these posterior vertebral structures can lead to facet joint irritation, stress fractures in the vertebrae, increased disc pressure and early disc degeneration.

Unfortunately, there is no highly reliable method for determining the presence of an anterior pelvic tilt and, if present, how severe it is. The lack of a reliable method for identifying this postural dysfunction has led to a number of erroneous theories and misconceptions about causes and treatment. Let's take a look at one of the more common erroneous theories.

It is a common misconception that an apparent leg-length discrepancy is caused by one innominate being excessively anteriorly rotated and "pushing" the lower extremity of that side in an inferior direction. If you envision a person supine on the treatment table, it's easy to see how one might come to that theory. If the innominate on the right side is anteriorly rotated, it seems that it might push the right lower extremity in an inferior direction and produce an apparent leg-length discrepancy.

The problem with this theory is that it discounts two key issues: the axis of rotation at the hip joint and the difference between pelvic movement in weight-bearing and non-weight-bearing positions.

Because the axis of rotation for an anterior pelvic tilt is at the hip joint, the pelvis rotates around the hip and therefore does not push the lower extremity in an inferior direction. Just as we would not expect the pinwheel to push its stem farther from the center, rotary movement around an axis does not cause the stem (lower extremity in our case) to be pushed inferiorly 

The assumption that an anterior pelvic tilt would push the lower extremity inferiorly also discounts the fact that when you are standing on the lower extremity, the pelvis physically cannot push the leg down. Instead, the pelvis rotates around the hip joint. A leg length discrepancy which is caused by muscle imbalance is far more likely to result from tightness in the quadratus lumborum muscle which pulls one side of the pelvis (right or left) higher. We will explore the ramifications of lateral pelvic tilt in another article.

The reason it is important to accurately understand the causes for these postural distortions is that our perception of their cause directs our treatment. A focus on the iliopsoas muscle as the primary cause for an apparent leg-length discrepancy would be unsuccessful when the true source of the problem is the quadratus lumborum.

In most cases, the anterior pelvic tilt is produced by dysfunctional muscular mechanics. Treatment should focus on reducing hypertonicity in the lumbar extensors and hip flexors. However, any treatment that reduces tightness in these muscles is unlikely to be successful by itself. Postural retraining is almost always an essential component to ensure that the same dysfunctional patterns are not repeated and re-engaged immediately after treatment.

Pelvic biomechanics can be challenging to accurately identify, but a fundamental awareness of these anatomical and biomechanical principles will help direct treatment in the right direction so the most beneficial results may be achieved.

 Article cited from: https://www.massagetoday.com/mpacms/mt/article.php?id=14831