Varus/valgus and internal/external torsional knee joint stiffness differs between sexes.
BACKGROUND
Torsional joint stiffness is thought to play a role in the observed sex bias in noncontact anterior cruciate ligament injury rates.


OBJECTIVE
Women will exhibit lower torsional stiffness values of the knee in response to varus/valgus and internal/external rotations than will men.


METHODS
Controlled laboratory study.


METHODS
Knee kinematics of 20 university students (10 men, 27.3 +/- 3.4 years, 177.3 +/- 6.8 cm, 81.1 +/- 7.0 kg; 10 women, 22.9 +/- 1.5 years, 169.0 +/- 7.1 cm, 66.1 +/- 11.4 kg) were measured while 0 to 10 N . m of varus and valgus torques were applied with the subject nonweightbearing and while 0 to 5 N . m of internal and external torques were applied with the subject nonweightbearing and weightbearing with the use of a custom joint testing device. Joint stiffness values were calculated at 1-N . m increments.


RESULTS
When low magnitudes of torque were applied to the knee, women had significantly lower stiffness values than did men. With the exception of applied external torque with the joint weightbearing and varus torque with the joint nonweightbearing, women demonstrated an increase in joint stiffness as the magnitude of torque increased from lower to higher magnitudes. In contrast, for the men, joint stiffness values remained unchanged as the magnitude of applied torque increased.


CONCLUSIONS
Women exhibited lower knee stiffness in response to low magnitudes of applied torque compared to men and demonstrated an increase of joint stiffness as the magnitude of applied torque increased.


CONCLUSIONS
The decreased stiffness behavior of the knee in response to low torques that was observed for women may have a role in detrimentally affecting knee biomechanics and resulting neuromuscular function, particularly when an individual transitions from nonweightbearing to weightbearing.
Applied Neuromechanics Research Laboratory, University of North Carolina, Greensboro, Department of Exercise and Sport Science, 250 HHP Building, Greensboro, NC 27402-6170, USA. rjschmit@uncg.edu
Randy J
RJ
Schmitz
Travis K
TK
Ficklin
Yohei
Y
Shimokochi
Anh-Dung
AD
Nguyen
Bruce D
BD
Beynnon
David H
DH
Perrin
Sandra J
SJ
Shultz
D000328:Adult; D016118:Anterior Cruciate Ligament / Q000503:physiopathology; D000070598:Anterior Cruciate Ligament Injuries; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology; D007719:Knee Joint / Q000502:physiology* / Q000503:physiopathology; D008297:Male; D016059:Range of Motion, Articular; D012016:Reference Values; D012737:Sex Factors; D054159:Torsion, Mechanical