PRACTICAL MATTER FOR CLINICIANS: Women Are Biomechanically Distinct From Men When They Run

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Learn how men and women are constructed differently—and therefore why they each have a distinctive running gait—to be better equipped to manage, and prevent, female-specific lower-extremity sports injury.

By Ray M. Fredericksen M.S. C-PED

Starting at puberty, sex hormones begin to affect changes in bone and lean body mass—changes that are different in females than in males. Typically, women have a broader pelvis, femoral anteversion (inward twisting of the femur), genu valgum (knees touch but ankles stand apart), and external tibial torsion (the feet do not line up straight because of outward rotation of the tibia). The center of gravity is slightly lower in women because they have a rounder, broader pelvis, although body type and height play a more significant role than gender. Women also have smaller bones and joint articular surfaces.¹

The most significant anatomical feature difference between the sexes, however, is the broader, wider pelvis of women, which facilitates childbirth. The difference in the anatomical structure of the lower extremity of women results in a greater quadriceps angle (Q angle), compared to men.

What is the Q Angle? Why Is It Important?

The Q angle is measured by drawing 2 lines (Figure):

1. a line that angles from the anterior superior iliac spine to the midpoint of the patella
2. a vertical line extending from the tibial tubercle to the femoral head.

The normative value is considered 13.5° (± 4.5°) for healthy individuals between 18 and 35 years of age. The Q angle in women is 6° to 8° greater than in men because of, as noted, women’s wider pelvis, increased femoral anteversion, and a relative knee valgus angle.

It has been hypothesized that the larger Q angle is a contributing factor to female athletes’ greater risk of injury (compared to men) in high-risk sports, such as running, soccer, and basketball.2 Women are known to have a higher incidence of noncontact anterior cruciate ligament (ACL) injury than men because they have a greater Q angle3; Malinski and colleagues4 proposed that women develop alternate neuromuscular motor-control strategies that contribute to their risk of noncontact ACL injury. I’ll return to discussing the importance of the Q angle later in this article.

Other Meaningful Female-Male Biomechanical Distinctions

Kinematic and kinetic studies in the literature have concluded that women tend to have less knee flexion and more knee valgus than men during the stance phase of the running gait. The literature further suggests that women have lower hamstring activation in comparison to men during the stance phase, which tends to increase load on the ACL. For example, In Malinski’s prospective study4 of 205 female athletes, the investigators determined that women are 4 to 6 times more likely than men to suffer ACL injury. Decreased valgus neuromuscular control and increased valgus joint loading are contributing factors in women for ACL injury in high-risk sports.

Women are also more susceptible than men to other lower-extremity injuries in high-risk sports, such as running, soccer, and basketball; their rate of injury is slightly higher. Runner’s knee, stress fracture, shin splints, iliotibial band syndrome, and back pain, for example, are more common in female runners.

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In a nutshell, women are built differently than men. They tend to have smaller and weaker muscles supporting the knees and greater muscle flexibility and ligamentous laxity of the joints. They typically have a larger hip width–femoral length ratio, which leads to greater hip abduction that can put them at greater risk of certain injuries because there is more motion at the hips and pelvis.

Research: The Female Q Angle, Ankle, and Foot

The greater Q angle of women also predisposes them to unique neuromuscular movement patterns at the joints of the ankle complex and of the foot, compared to men. Women have smaller bone dimensions and lower bone density as they age, further contributing to risk of injury.5 Several studies have shed light on the biomechanical and anatomical distinctiveness of women:

Study #1. It is generally accepted that women experience a greater pronation angle during footstrike than men. In a study using a 3-dimensional (3-D) kinematic analysis technique of the ankle joint, Sinclair and co-workers6 reported that college-age female runners have a higher angle of ankle inversion–eversion motion than males; females also have greater joint mobility and ligament flaccidity of the foot.

Study #2. Fredericksen, in a master’s degree thesis,7 built a 3-dimensional kinematic model of the rearfoot and forefoot to describe the motions of the calcaneus and first metatarsal ray during the stance phase of running gait. A Nike Presto model running shoe with a Velcro midfoot strap was used, so that the overlays of the shoe could be stripped away, thus exposing the bones of the foot. Retro-reflective targets were built in a triad arrangement, adhered directed to boney landmarks of the calcaneus and first metatarsal ray of the foot. Using marker positions from a static trial, a rigid body reference model was defined for the foot and Euler angles extracted to calculate motion of the midtarsal joint about the mediolateral axis of the foot.

A greater inverted contact angle was observed in female participants, compared to males during heelstrike, resulting in an overall greater eversion angle at midstance of 15° to 18° in females, compared to 9° to 12° among males. During midstance, as heel lift was initiated, a rapid, greater inversion angle of 10° to 12° was observed in the female runners, compared to 8° to 10° in males.

Study #3. In a study using a 3-D Qualysis motion-capture system, Emami and colleagues8 constructed a rigid body-segment model of the ankle joint, midfoot, and metatarsus. Joint moments were computed in visual 3D using inverse dynamic values. The investigators observed a resistive adduction moment in female runners that was twice as high as in male participants—suggesting a rapid supinatory twist at the midtarsal as runners increase plantar flexion of the first metatarsal and hallux during the propulsion phase of gait. Emami further postulated that this was a neuromuscular motor response by women to reduce medial load at the knee joint to compensate for their greater Q angle.

Research: Shoe Design and Orthotics

Study #1. A confidential, subjective wear-test analysis of 300 pairs of women’s running shoes, undertaken by Brooks Running Shoes in 1990, led to the launch of the gender-specific footwear line “Brooks for Women.” In this analysis, 80% of shoes with ≥300 miles of wear showed significant wear at the lateral heel area and varying degrees of wear along the lateral forefoot. The term corkscrewing was used to describe the combination of (1) medial breakdown in the rearfoot of the shoe midsole and upper and (2) lateral deviation of the upper in the forefoot.

Study #2. A biomechanical study of female gait patterns, sponsored by Brooks, was conducted by Soutas-Little and colleagues.9 Thirty female recreational runners of college age or older were recruited for the study. 3-D kinematic data were collected simultaneously as runners ran across an ASTM forceplate at a controlled speed of 7.2 miles per hour. Anthropometric data were also measured for the foot, shank, femur, and Q-angle of each participant.

Five significant trends were observed from the Soutas-Little study that led to development of the “Brooks for Women” product line in the mid 1980’s.

• Women tend to pronate more than men at footstrike because they produce a greater contact angle and have a larger Q angle.
• Women exhibit a greater inversion rate and angle during resupination of the foot than men, suggesting a compensatory response to their larger Q angle to minimize loads at the knee joint.
• The trend observed in female gait patterns is proportional to the leg length–pelvis width ratio (women with shorter legs and a wider pelvis exhibit the trend to a greater degree).
• Women have a greater forefoot width–heel width ratio than men.
• Women are generally more flexible than men, with more joint flaccidity; this flexibility contributes to greater mobility of the joints that constitute the lower extremity.

It is now a generally accepted medical proposition that women require a support platform that is distinct from what men require. Manufacturers have, in turn, been quick to address this formidable market. See “Athletes Lead, Manufacturers Follow,” page 26, for a capsule examination of female-targeted footwear and insoles.

What Is the Clinical Relevance of These Differences?

Gender-based anatomical differences in running gait result in unique neuromuscular movement patterns for women that can put them at greater risk of injury in high-impact activities, such as running, soccer, and basketball. Example: Women’s greater Q angle has been cited as a major contributor to a higher incidence of ACL injury in women than in men.

It has been suggested that women develop compensatory movement patterns during footstrike to reduce load at the knee joint. However, these movement patterns can, eventually, lead to an increase in other overuse injuries (eg, plantar fasciitis, Achilles tendinitis), as protective modalities, such as footwear, break down.

Footwear and insole companies are actively competing to create gender-specific designs that address the female athletic footwear market. Knowledge of which products on the market specifically address the needs of the female athlete can aid you in the prevention and treatment of gender-specific injuries.

Ray M. Fredericksen, MS, CPed, is sole proprietor of Sports Biomechanics, Inc.

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