What is natural anterior pelvic tilt?Photo by gtall1

In most cases, when we talk about anterior pelvic tilt we actually mean excess anterior pelvic tilt. Since the human spine is not a straight line but has a slight S-shape, some degree of anterior pelvic is natural and even desirable. Men generally have a lower degree of pelvic tilt than women. But how much anterior pelvic tilt is still natural?

According to some physiotherapists, men should have a forward pelvic tilt of 0-5 degrees. For women, the natural range is said to be 7-10 degrees. There is, however, disagreement over whether this numbers are correct, as different studies have yielded different results.

Studies that include both men and women generally show a wider range of pelvic angles. For example, one study with 54 healthy males and females reported a range of 3–22 degrees (1), while another study with low back pain patients found a very similar range of 4–21 degrees (2). In a third study, the range was between -9 (posterior tilt) and 12 (anterior tilt) degrees (3).

Although the range in the third study is as wide as in the first two, neutral pelvic position appears to have been defined differently in the third study. All in all, when both sexes are included, the amount of pelvic tilt can vary up to about 20 degrees from one individual to another.

When we look at men and women separately, the ranges of pelvic tilt become somewhat narrower. A large study with 118 adults found that anterior pelvic tilt ranged from 3.0 to 18.0 degrees in men and 2.0 to 19.0 in women (4). Mean pelvic tilt was 9.6 in men and 11.7 in women.

A smaller study reported a mean anterior pelvic tilt of ~4 degrees in women and ~2 degrees in men, with standard deviations of less than one degree (5). In this study, people who had suffered a cruciate ligament injury had a more pronounced anterior pelvic tilt than those without previous injuries. Cruciate ligaments occur in several joints of the body, such as the knee.

So why the discrepancy between the results from different studies? Part of the reason is in the method of measurement. Currently, there is no "gold standard" of measuring pelvic tilt. Rather, there are several different ways that give somewhat different results. Furthermore, different people using the same method may get different numbers. One study showed that measurement error varies considerably between testers, and that training and experience are required to achieve measurement reliability and accuracy between multiple testers (6).

The difference in the natural range of pelvic tilt between men and women is related to skeletal differences. The pelvic cavity has a different shape in women, and their hip joints are smaller and forward-facing. Women also have shorter arms and legs relative to height and smaller bones in general. As a result, women naturally have a slightly lower center of gravity and a different posture during standing, sitting and moving.

Another explanation for why women have a more pronounced anterior pelvic tilt is because their bodies are designed to carry a child in the womb. During pregnancy, the degree of anterior pelvic tilt typically increases. In one Korean study, pregnant women had a mean maximal anterior pelvic tilt of 21 degrees, whereas non-pregnant women had a mean maximal anterior pelvic tilt of 15 degrees (7). The increased tilt may sometimes result in lower back and pelvic pain during pregnancy.

Accurate measurement requires a visit to the doctor or a physiotherapist, and as we've seen, even then the results might be quite different from those seen in the studies. A professional probably could, however, tell you whether your pelvic angle falls in what they consider a common range or whether you're a statistical outlier.

A very crude way of measuring your anterior pelvic tilt is to stand with your back against the wall and see how much space there is between the lower back and the wall. You can use a mirror or try it with your hands. If the space is big enough to fit your entire fist, that is probably a sign of excess anterior pelvic tilt.

References

1. Kroll PG, Arnofsky SL, Peckham S, Rabinowitz A. The relationship between lumbar lordosis and pelvic tilt angle. J Back Musculoskeletal Rehabil. 2000;14: 21–25.

2. Gilliam J, Brunt D, MacMillan M, Kinard RE, Montgomery WJ. Relationship of the pelvic angle to the sacral angle: Measurement of clinical reliability and validity. J Orthop Sports Phys Ther. 1994;20: 193–199.

3. Deusinger RH. Validity of pelvic tilt measurements in anatomical neutral position. J Biomech. 1992;25: 764

4. McKeon J, Hertel J. Sex Differences and Representative Values for 6 Lower Extremity Alignment Measures. Journal of Athletic Training. 2009, 44 (3): 249–255. 

5. Hertel J, Dorfman JH, Braham RA. Lower extremity malalignments and anterior cruciate ligament injury history. J Sports Sci Med. 2004; 3(4): 220–225.

6. Shultz SJ, Nguyen AD, Windley TC, Kulas AS, Botic TL, Beynnon BD. Intratester and intertester reliability of clinical measures of lower extremity anatomic characteristics: implications for multicenter studies. Clin J Sport Med. 2006; 16(2): 155–161.

7. Oh SY, Yoo JY, Ha SB, Won HS. Dynamic Imbalance of Lumbo-Pelvic Motion in Pregnant Women with Back and Pelvic Pain. J Korean Acad Rehabil Med. 2001; 25(5): 855-860.

What is posterior pelvic tilt?Photo by bupowski

Like anterior pelvic tilt, posterior pelvic tilt is a postural is a postural deficiency, although a less common one. Unlike in anterior pelvic tilt, however, in posterior pelvic tilt the top of the pelvis is tipped backward instead of forward.

The image below shows a neutral pelvic position (left), a pelvis with posterior pelvic tilt (middle) and a pelvis with anterior pelvic tilt (right):

Neutral pelvis, posterior pelvic tilt and anterior pelvic tilt

As can be seen from the pictures, it is the position of the top of the pelvis, not the bottom, that determines whether the tilt is anterior (i.e. forwards) or posterior (i.e. backwards). Whereas anterior pelvic tilt involves an exaggeration of the natural lumbar curvature (the S-shape of the spine), posterior pelvic tilt is a reduction in the natural lumbar curvature.

The muscles involved in posterior pelvic tilt are hip extensors, hip flexors and abdominal muscles. Contrary to anterior pelvic tilt, the hip extensors are shortened and the hip flexors are laxed. The abdominal muscles are tightened.


Most of the exercise advice on fixing anterior pelvic tilt is focused on stretches and strength training. Cardiovascular exercise, on the other hand, rarely gets a mention. So is doing cardio worth the while?

Usually, when we talk about pelvic tilt (be it anterior or posterior), we mean the degree of the tilt of the pelvis during standing still. However, the same tilt is evident during cardio exercises such as running as well. As a result, the spinal curvature increases during running, which may cause lower back pain in runners.

There is evidence to suggest that too much pelvic tilt is linked to injuries around the hip and lower back area (1). Furthermore, these injuries account for 14% of all injuries in distance runners and sprinters (2).

This suggests that doing aerobic exercise, especially running, in itself will not fix anterior pelvic tilt. In fact, it may even worsen the problem by stressing the excessively curved spine and causing lower back pain. It is better to deal with the excess tilt before engaging in distance running or sprinting.

To determine your own anterior pelvic tilt during running, it is best to ask someone to observe you run. The curvature of your spine and the movement of the pelvis gives a rough idea of whether you're leaning more towards anterior or posterior pelvic tilt. Another method is to take a video of yourself running an watch it in slow motion. The video below shows an example of posterior and anterior pelvic tilt during running:




The method of running will also determine whether back pain or other injuries will occur in time. Currently, there is a lot of debate whether barefoot running (or wearing shoes that emulate barefoot running, such as Vibram FiveFingers) results in a more natural gait and thus less injuries than wearing shoes with a lot of heel support. There is, however, limited evidence to prove either way.

If you have excess anterior pelvic tilt, trying out different shoes may help to relieve or eliminate pain during running. However, it is recommended to fix anterior pelvic tilt before engaging in any serious running. Note that not all of the exercises commonly recommended are in fact related to anterior pelvic tilt. For example, no connection between abdominal muscle strength and pelvic tilt has been found so far.

References

(1) Geraci MC. Overuse injuries of the hip and pelvis. Journal of Back and Musculoskeletal Rehabilitation 1996;6:5-19.

(2) Bennell KL, Crossley, K. Musculoskeletal injuries in track and field: incidence, distribution and risk factors. Aust J Sci Med Sport 1996;28:69-75.


According to common knowledge, one of the key muscles in anterior pelvic tilt are the abdominal muscles. The most prominent of these muscles is the rectus abdominis, a paired muscle that runs vertically on both sides of the abdomen:

The rectus abdominis muscles

The rectus abdominis muscle is what you see when someone has a "sixpack". Since the ambdominal muscles are involved in tilting the pelvis backwards (i.e. posterior pelvic tilt), it has been assumed that the strength of these muscles is related to the degree of anterior pelvic tilt during standing.

Anatomically, this idea makes sense on the surface. In anterior pelvic tilt, where the pelvis is tilted forwards, the abdominal muscles would appear to be stretched downwards, which would in turn cause them to lengthen and become weak over time. This is why several people, including physiotherapists, recommend training the abdominal muscles when there is an excessive anterior pelvic tilt.

The problem is that it's based on a anatomical hypothesis of what should happen when the pelvis is tilted forwards, not what actually happens. Empirically, it remains to be proven that abdominal muscle strength is related to anterior pelvic tilt in any way. Furthermore, even if abdominal muscle weakness did correlate with anterior pelvic tilt, it would not prove that training the muscles would fix anterior pelvic tilt.

One of the standard ways of measuring abdominal muscle strength is the leg-lowering test. To perform the leg-lowering test, lie on your back and raise your feet into the air so that your torso and legs are in a 90 degree angle and your knees are straight. Flatten your spine to the ground. Then, lower your both legs together while keeping your knees straight and your back flattened against the ground. The lowering part should take 10 seconds. The point where you notice your lower back start to arch or come off the ground is the cut-off point for the test. Here's a video showing the leg-lowering test:


In one study, 31 healthy men and women were measured for abdominal muscle strength, lumbar lordosis (i.e. the curvature of the spine) and pelvic tilt (1). To measure abdominal muscle strength, the leg-lowering test was performed. The correlation between the variables was so low that according the authors, abdominal muscle function, lumbar lordosis and pelvic tilt were not linked.

Part of the reason for this lack of link is that the abdominal muscles are not active during standing and walking. The strength or weakness of the abdominal muscles is therefore not likely responsible for the degree of pelvic tilt or lumbar lordosis, even though this relationship has often been assumed.

The authors note that while the leg-lowering test is a standard test for measuring abdominal muscle function, it has not been proven to measure muscle strength accurately. A different measurement might have given different results. Furthermore, the length of the abdominal muscles was not measured. Thus, it is possible that the structure of the abdominal muscles is involved in pelvic tilt and lumbar lordosis.

What this study does show, however, is that much of the information out there on anterior pelvic tilt is not based on empirical evidence.

References

(1) Walker ML, Rothstein JM, Finucane SD, Lamb RL. Relationships Between Lumbar Lordosis, Pelvic Tilt, and Abdominal Muscle Performance. Physical Therapy, 1987; 67(4): 512-516.