Pelvic size matters

female injury risks due to bone structures

There is an old saying in the asian culture “big bottoms produce great kids”. Therefore, pelvic and bottom size is one important aspect to the ancestors when choosing their daughter-in-law/grand-daughter-in-law.

In structure, there are pelvic differences between gender, which have their pros and cons. This article aims to discuss female pelvic structure and the influence on kinesiology and daily functions.

Pelvic structure diversity between sex

Male: the upper outlet is rounder (red virile). Pelvic crest (wall of the pelvis) is steeper (blue line).

Female: the upper outlet is oval shaped, the circumference is wider than men (red circle). Pelvic crest is more inclined (red line).

Male: the inferior outlet is narrower, triangular shaped.

Female: the inferior outlet is wider and rounder than males.

Figure origin: 骨盆完全指南

Male: the border of the pelvic crest is narrower and sharper (blue margin). The tailbone is immobile.

Female: the border of the pelvic crest is wider and rounder (red margin). The tailbone is slightly mobile.

Figure origin: 骨盆完全指南

Advantages of wide pelvis

Women pelvic size and structure is built for childbirth. The wide upper and lower outlet of the pelvis create an safe environment for the baby to grow. With female hormones, the tailbone is mobile to increase space.

Disadvantages of wide pelvis

Pelvis structure influences the anatomy of the pelvic muscles. While the female pelvis is suitable for bearing children, there are functional disadvantages when it comes to daily activities and sports.

The Q angle is measured between the force line of quadriceps muscle (dotted line) and the vertical line (solid line) and can be predicted from the width of the pelvis. Wide pelvis is highly related with larger Q angle.

The greater the area between two lines (blue area), the more disperse of quadriceps force production. Additional pressure to the knees can be a result of large Q angle. When compared with men, women tend to have larger pelvis and result in greater Q angle. Thus, the injury risk of the lower limbs is higher.

According to previous kinematic studies, women tend to knock their knees (arrow in the figure below) during landing and single leg squat, putting stress on knee ligaments and joints. This reflects instability in the lower extremities and is highly related with greater Q angle.

With the unwanted stress added, women have a higher risk of anterior cruciate ligament injury.

When analyzing walking movement between genders, the women tend to have greater inclination of the pelvis than men. This is related with pelvic muscle strength and control.

In structure, men have a cylinder shaped pelvis which the hip and pelvic muscles are more condensed and produce greater power. In contrast, women have a funnel shaped pelvis with separated pelvic muscles, therefore decreasing the efficiency of muscle force production.

Greater pelvic inclination during walking is linked with greater instability in the pelvic area. This can result shear force in the low back, causing low back pain.

Left: figure of pelvic inclination. Right: figure of pelvic form between sex.

The pelvic differences are evident between genders, which impact differently in function. While the pelvis is designed for having children for women, the muscle performance and stability are inferior to men.

**Check out the previous articles for pelvic and hip exercises***

Glute training: Why do you need to train your glutes?

Hip adductor training: The inner thighs: workout boosters

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References:

Hannigan JJ, Osternig LR, Chou LS. Sex-Specific Relationships Between Hip Strength and Hip, Pelvis, and Trunk Kinematics in Healthy Runners. J Appl Biomech 2018 Feb 1;34(1):76–81.

Howard JS, Fazio MA, Mattacola CG, Uhl TL, Jacobs CA. Structure, sex, and strength and knee and hip kinematics during landing. J Athl Train 2011;46(4):376–85.

Graci V, Van Dillen LR, Salsich GB. Gender differences in trunk, pelvis and lower limb kinematics during a single leg squat. Gait Posture 2012 Jul;36(3):461–6.

Smith LK, Lelas JL, Kerrigan DC. Gender differences in pelvic motions and center of mass displacement during walking: stereotypes quantified. J Womens Health Gend Based Med 2002 Jun;11(5):453–8.

竹內京子、岡橋優子。(2013)骨盆完全指南(初版,p.22)。楓葉社文化。

Netter FH. Atlas of human anatomy 4th edition.

物理治療師 女性運動與姿勢矯正 physiotherapist, MS, CES