Numerous studies have been conducted on changes of knee ligament laxity during the menstrual cycle (MC) since there are more injuries in certain phases. Some researchers believe that since estrogen receptor β exists in ligaments and tendons in the knee, estrogen may modulate towards a state of laxity. However, increased tissue temperature also observed during the MC can predispose ligament and tendon laxness. The number of women using oral contraceptive pills (OCP) has constantly increased in the United States. This exogenous source of synthetic forms of steroid hormones prevents ovulation by maintaining more consistent daily hormone levels than occurs. Since the estrogen receptor β exists on human connective tissue, OCP might have an impact on tendon and ligament synthesis, structure, and biomechanical properties. Therefore, the purpose of this study was to assess in women the relationship between Estradiol (E2) serum concentrations and tissue temperature during the MC and their combined effect on ACL elasticity, force to flex the knee (FFK), and knee flexion-extension hysteresis (KFEH) in OCP users and non-OCP users. Nineteen non-athletic young healthy females were divided into two groups; OCP users and non-OCP users. E2 serum concentrations, ACL elasticity, FFK, and KFEH were assessed both at ambient temperature (22 °C) and after 38 °C warming of the leg to stabilize the normal temperature during the MC. The result of this investigation showed that ACL elasticity was significantly lower and FFK and KFEH were significantly higher during ovulation compared to menstruation (p<0.05) but after 38 °C warming of the leg, there were no differences in KKF and KFEH in non-OCP users. Also, ACL elasticity was significantly lower and FFK and KFEH were significantly higher OCP users than non-OCP users (p<0.05) at ambient temperature. But, no significant difference in FFK and FFEH between the two groups was found after warming to 38 °C. In conclusion, OCP users have more knee stiffness and effect of heat on FFK and KFEH when their legs were heated compared to non-OCP users. In addition, ACL elasticity, FFK, and KFEH were affected not only by estrogen but tissue temperature during the menstrual cycle.

LLU Discipline

Physical Therapy


Physical Therapy


School of Allied Health Professions

First Advisor

Petrofsky, Jerrold S.

Second Advisor

Berk, Lee S.

Third Advisor

Brandon, Karen

Fourth Advisor

Daher, Noha S.

Fifth Advisor

Laymon, Michael S.

Degree Name

Doctor of Science (DSc)

Degree Level


Year Degree Awarded

January 2013

Date (Title Page)




Library of Congress/MESH Subject Headings

Ligaments, Articular; Physical Therapy Modalities; Contraceptives, Oral; Oral contraceptives - side effects; Menstruation

Subject - Local

Anterior Cruciate Ligament Elasticity; Muscle flexibility; Tendon flexibility; oral contraceptives; menstrual cycles



Page Count

92 p.

Digital Format


Digital Publisher

Loma Linda University Libraries

Usage Rights

This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.


Loma Linda University Electronic Theses & Dissertations

Collection Website



Loma Linda University. Del E. Webb Memorial Library. University Archives