“To our knowledge there exists no study comparing knee and hip joint adduction angles and impulses between males and females with a high training volume.” — principal study authors, University of Freiburg in Germany.
Indeed, while sports medicine doctors can anecdotally attest to the different injury patterns and tendencies based on gender, actual study data has been essentially non-existent until this group of intrepid researchers designed the study protocol, raised the funds and went to work.
“The purpose of the present study was to determine whether hip and knee joint kinematics and kinetics in runners with a high weekly mileage are gender-specific over a range of running speeds. Specifically, we hypothesized that women would demonstrate increased knee and hip adduction loading.”
Gender Injury Patterns Make a Huge Difference
Although girls and women are leveling the playing field by participating in a wider variety of sports at higher levels, the field remains uneven especially in terms of injuries. When it comes to running, a Vancouver area sports injury clinic found that women represented 54% of injuries while men represented 46% of injuries after evaluating about 2, 000 patients in 2002.
According to Runners Connect, a website that shares information and helpful tips about running, women are 50% more likely to suffer from patellofemoral pain syndrome or runner’s knee, iliobital band syndrome, stress fractures, medial tibial stress syndrome or shin splints, Achilles tendonitis, and plantar fasciitis. Although it appears that female runners are more injury-prone than male runners, few studies have been conducted to examine the gender-specific running patterns that may be responsible.
In 1978, Cutting et al. found that the gender of a walker can be determined through a kinematic assessment. Titled “A Biomechanical Invariant for Gait Perception, ” the study focused on the perception and psychophysics of the human gait. Since then, several studies have been published concerning gender-specific gait patterns and have found a specific skeletal motion associated with each gender.
Despite the well-documented locomotion patterns of men and women while walking, the differences between sexes while running remains relatively obscure. In 2003, Ferber et al. found that women had significantly higher hip adduction angles and knee abduction angles. However, all the participants were evaluated at one predefined running speed so further differences were not evaluated as physical demand increased. In 2008, Chumanov et al. evaluated the hip joint in men and women as they walked and ran at different speeds and inclinations. However, the study only looked at kinematics and kinetics of that specific joint, leaving other joints unevaluated.
The Groundbreaking University of Freiburg Study
Dominic Gehring, Ph.D.; Guillaume Mornieux, Ph.D.; Jana Fleischmann; and Albert Gollhofer, Ph.D. authored the study titled “Knee and Hip Joint Biomechanics are Gender-specific in Runners with High Running Mileage.” Published in 2014 in the International Journal of Sports Medicine, the study evaluated 32 individuals with high training volume. Each participant ran over 50 kilometers per week and were known rearfoot strikers, meaning their heels hit the ground first when running. The 16 men and 16 women were healthy and suffered no injuries during the 12 months preceding the study.
To evaluate the gait, cadence, and kinematics of each participant, the doctors installed a 3D-motion analysis system on a 35-meter track. The motion analysis system consisted of 12 near-infrared cameras that recorded the kinematics of each runner’s right leg. A force plate was also installed on the track and the participants were to run over it at three predetermined speeds, 3 m/s, 4 m/s, and 5 m/s. The doctors had the athletes run 10 trials at each speed. All athletes wore the same standard running shoe when being evaluated.
“Each participant performed 10 valid running trials in each speed condition. A trial was considered to be valid when the right foot came into complete contact with the force plate, the participant maintained the correct speed and a natural running style was retained, ” the study explains. “High-speed videos were used to verify that the intended rearfoot strike pattern was apparent in all subjects.”
All the participants also wore retro-reflective markers on the rearfoot, shank, thigh, and pelvis of their right side. Markers were also attached to anatomical landmarks like the greater trochanter, part of the femur; the posterior and anterior superior illiac spines, part of the wing of the pelvis; the malleolus, the bony protuberance of the ankle; the tibia; and parts of the knee. The doctors also placed markers on the heel cup and toe box of the shoe. These markers helped the researchers determine the length of the bone segments and the location of the joints.
Study Protocol
The doctors first performed a static standing trial to determine the segment length and joint centers in each participant. The athletes then ran across the track at a predetermined speed. The researchers used a Joint Coordinate System approach engineered by Grood and Suntay to determine joint kinematics. Specialized software computed the kinematic and kinetic information by evaluating the joint movements and ground contact of each participant’s legs and feet.
Results
After the doctors let the athletes and computer system run, they found significant differences in the joint kinetics between the male runners and female runners.
“The impact peak of the hip adduction moment was significantly increased in women. Results revealed that the gender difference was even more pronounced at 5 m/s than at 3 m/s running speed, ” the researchers explained.
The doctors also found that, unlike the hip joint, the knee adduction movement at the impact peak and mid-stance peak were not significantly different between the sexes. No general difference was found when comparing entire joint loading. However, a difference existed when comparing gender and speed. The joint impulses in women running at 3 m/s and 4m/s were at the level of men running at 5m/s.
In addition to finding that women’s ground contact time was generally shorter than men’s, the doctors also discovered notable differences in the joint kinematics of the male and female athletes.
“Female runners showed a significantly more adducted initial and peak hip angle at all running speeds, ” the study explained. “In contrast, the women’s frontal plane knee position at initial contact as well as for peak angle was in general less adducted than that of men.”
After evaluating the kinetic and kinematic differences between men and women, the doctors determined that women exhibit increased hip adduction positioning and reduced knee adduction positioning.
“An increase in the hip adduction angle may likely cause an increased lever arm at the knee and hip joint level, which would consequently lead to increased joint adduction moments, ” the doctors explain. “The results of the present study revealed that female runners exhibit a 4–5° more pronounced adducted hip position at initial ground contact as well as during mid-stance at slow and at fast running speeds than men. This in turn may therefore be an explanatory model of the significantly increased hip adduction moments as well as the trend for increased knee adduction moments in females.”
These increased impact adduction joint moments were observed in the female athletes regardless of the speed at which they were running. Increased adduction impulses are often associated with overuse injuries and may be the culprit behind gender-specific injury risk. Further studies are required to pinpoint the reason for gender-specific injuries in running and determine whether the study’s results are related to the risk of common overuse injuries.
The study also confirms and extends the results Chumanov et al. obtained in 2008. Running speed and gender differences in frontal plane hip kinematics are independent of each other. The researchers showed that gender differences in frontal plane knee and hip joint kinematics are maintained regardless of distance travelled and running speed.
Conclusions and Lessons
“First, this expands the previously existing knowledge of gender-specific running patterns to runners with a high training volume who are known to suffer the most from overuse injuries, ” the doctors wrote. “Second, these results support the theory that, independently of running speed and running expertise, gender differences in frontal plane hip and knee kinematics are systematically present.”
Despite not finding a direct causation for gender-specific running injuries, the University of Freiburg researchers have made progress in unraveling the knee and hip joint mechanics of men and women. Their extensive study lays the groundwork for a better understanding of gender-specific running patterns and gender-specific injury risk that can help both male and female runners improve their stride.
