What Is Natural Anterior Pelvic Tilt?
Photo by gtall1In 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.
