The differential effects of gender, anthropometry, and prior hormonal state on frontal plane knee joint stiffness

Martha L. Cammarata, Yasin Y. Dhaher*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


Background: Gender differences in passive frontal plane knee stiffness may contribute to the increased anterior cruciate ligament injury rate in females. Gender-based stiffness differences have been attributed to anthropometric variations, but little data exist describing this relationship. Furthermore, sex hormone levels appear to influence joint stiffness, but the differential effects of instantaneous and prior hormonal concentrations remain unknown. This study sought to explore the effect of gender, prior hormonal status, and anthropometry on passive frontal plane knee joint stiffness. Methods: Twelve males and 31 females participated. Females were grouped by hormonal contraceptive use (non users [n = 11], monophasic contraceptive users [n = 11], and triphasic contraceptive users [n = 9]) and tested at the same point in the menstrual cycle. Subjects' right knee was passively stretched ±7° in the frontal plane at 3°/s. Stiffness was estimated at three loading levels and normalized by body size to minimize anthropometric biases. A 4 (group) × 3 (load) repeated measures analysis of variance was performed for both raw and normalized stiffness. Linear regression analyses were preformed between stiffness estimates and knee diameter and quadriceps femoris angle. Findings: Males displayed significantly greater (P < 0.05) frontal plane stiffness than females. When normalized, males displayed significantly greater stiffness in valgus (P < 0.05), but not varus (P > 0.05) than females. No significant effect (P > 0.05) of prior hormonal state was found; however, when normalized, varus stiffness was significantly less for triphasic contraceptive users than the other female groups (P < 0.05). Quadriceps femoris angle was negatively correlated and knee diameter was positively correlated to knee stiffness. Interpretation: Consistent with earlier in vitro findings, our data may indicate that ligament material properties are gender specific. A deficit in passive knee joint stiffness may place a larger burden on the neuromuscular system to resist frontal plane loading in females.

Original languageEnglish (US)
Pages (from-to)937-945
Number of pages9
JournalClinical Biomechanics
Issue number7
StatePublished - Aug 2008


  • Contraceptives
  • Frontal plane
  • Gender
  • Hormones
  • Knee stiffness

ASJC Scopus subject areas

  • Biophysics
  • Orthopedics and Sports Medicine


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