Variations in dynamic knee valgus and gluteus medius onset timing in non-athletic females related to hormonal changes during the menstrual cycle ☆ Guilherme Manna Cesar a, ⁎, Vanessa Santos Pereira a , Paulo Roberto Pereira Santiago b , Benedito Galvão Benze c , Paula Hentshel Lobo da Costa d , César Ferreira Amorim e , Fabio Viadanna Serrão a a Department of Physical Therapy, Federal University of São Carlos, São Carlos, SP, Brazil b Department of Physical Education, State University of São Paulo UNESP, Rio Claro, SP, Brazil c Department of Statistics, Federal University of São Carlos, São Carlos, SP, Brazil d Department of Physical Education and Human Motricity, Federal University of São, Carlos, São Carlos, SP, Brazil e Department of Mechanical Engineering, State University of São Paulo UNESP, Guaratingueta, SP, Brazil abstract article info Article history: Received 15 July 2009 Received in revised form 5 May 2010 Accepted 5 May 2010 Available online xxxx Keywords: Dynamic valgus Anterior cruciate ligament (ACL) Kinematics Electromyography (EMG) Menstrual cycle It has been suggested that activities of daily living could contribute to the occurrence of ACL injury in females. Currently, no studies have focused on the lower extremity behavior of a non-athletic population to compare or understand the lower extremity adeptness towards daily movements that mimic athletic tasks. Our hypothesis was that increased knee valgus angles would occur during the late follicular phase of the menstrual cycle accompanied by different onset timing of the gluteus medius muscle. In a controlled laboratory study, 23 non-athletic collegiate females participated and 15 subjects comprised the final sample for statistical analysis. Subjects performed a single leg drop landing maneuver while 3-D knee kinematics and gluteus medius muscle onset timing were assessed throughout three distinct phases of the menstrual cycle, confirmed by blood hormone analysis. In general, knee valgus angles were significantly less in the luteal phase compared to both follicular phases (p b 0.005), while differences were not observed for gluteus medius onset timing (p = 0.936). As a decreased knee joint valgus angle was observed during the luteal phase, it was hypothesized that the hormone progesterone could significantly influence knee kinematics during a dynamic task. However, such influence was not observed for gluteus medius EMG onset timing as a significant correlation between gluteus medius onset timing and knee valgus angle could not be determined. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Many studies have reported differences between male and female knee joint kinematics during various activities. [1–7] Russell et al. [8] investigated the difference in frontal plane knee angle of 16 healthy males and females during a jumping task. The authors reported higher knee valgus angles for the female subjects, suggesting that these higher valgus angles may predispose females to a higher incidence of anterior cruciate ligament (ACL) injury. Other studies have demon- strated the effect of female sex hormones (e.g. estrogen) on the ACL tissue, leading to an increased laxity and consequent increased risk of injury [9–11] when such hormones are at their peak levels. However, very few studies [12,13] assessed such purported laxity during a dynamic task throughout different aspects of hormonal milieu. It should be stressed that since injuries most often occur during dynamic tasks, it is of great importance to also assess joint excursions during the different phases of the menstrual cycle dynamically. According to Childs, [14] falls and motor vehicle accidents greatly contribute to the occurrence of ACL injuries in the United States, which could be as high as 250,000 occurrences per year. Though most ACL injuries occur in an athletic environment, cases from a non- athletic population usually happen during activities of daily living (28.1%) and recreational activities (60.1%). [15] In turn, the surgical interventions and rehabilitation costs associated with medical treatment of such ACL injuries could greatly contribute to the economic burden placed on the health system. As yet no studies have focused on the lower extremity behavior of a non-athletic population to either compare it to athletes or simply understand the lower extremity adeptness towards various daily movements that mimic athletic tasks (e.g. changing directions, stepping off a platform, and perform a single leg land, among others). Moreover, no studies have investigated the pattern of onset timing of the gluteus medius muscle which is one the major muscles that control the coronal plane movement of the thigh during the different phases of the menstrual cycle. Since the contraction of the gluteus medius muscle abducts the thigh, it consequently contributes to the control of knee valgus during The Knee xxx (2010) xxx–xxx ☆ All authors were fully involved in the study and preparation of this manuscript and the material within has not been and will not be submitted for publication elsewhere. ⁎ Corresponding author. Rua Agnello Marchi, 326. Vila Oliveira. Mogi das Cruzes, SP 08790-290, Brazil. Tel.: +55 11 7232 2844; fax: +55 11 4796 7228. E-mail address: guilhermemanna@yahoo.com (G.M. Cesar). THEKNE-01346; No of Pages 7 0968-0160/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.knee.2010.05.004 Contents lists available at ScienceDirect The Knee ARTICLE IN PRESS Please cite this article as: Cesar GM, et al, Variations in dynamic knee valgus and gluteus medius onset timing in non-athletic females related to hormonal changes during the menstrual cycle, The Knee (2010), doi:10.1016/j.knee.2010.05.004