The association of the menstrual cycle with the laxity of the anterior cruciate ligament in adolescent female athletes

Knee Laxities Changes with Sex-steroids throughout the Menstrual Cycle Phases in Athlete and Non-athlete Females

Objective:  Our study investigated changes of knee laxities in athletes and non-athletes females and relationship between knee laxity and sex-steroid at menstrual cycle phases. Methods:  Forty six healthy females, twenty four athletes and twenty two non-athletes not on hormone contraceptive pills, had no previous knee injuries and with regular menstrual cycles for 3 consecutive months, participated in the study. Medial and lateral knee laxities were determined by varus-valgus tests at follicular, ovulatory and luteal phases. Serum level of relaxin, estrogen, progesterone and testosterone were determined by ELISA and radioimmunoassay. Results:  Knee laxities in athletes and non-athletes at 0° and 20° flexion were the highest in luteal phase with non-athletes possess greater laxity than athletes. Positive correlation between progesterone and relaxin levels with knee laxities were observed. Meanwhile, the levels of both hormones were highest in the luteal phase. Conclusion:  Increased medial and lateral knee laxities in athletes and non-athletes associated with high serum progesterone and relaxin levels in luteal phase may contribute toward increased risk of non-contact knee injury. However, lower knee laxity in athletes than non-athletes suggest that exercise could be a protective factor.

The influence on menstrual cycle phases on trunk flexion mobility assessed with finger floor distance test: a preliminary study

Background: The menstrual cycle plays an important role in a woman's body and the relationship between different phases of the menstrual cycle and flexibility has not been well known. Aim of the study: This study aimed to examine whether the different phases of the menstrual cycle could affect trunk flexion mobility in young, healthy, physically active women who had not used hormonal contraception and had not received hormone treatment. Material and methods: In total, ten healthy female nulliparas aged 25 - 30 participated in the study. The inclusion criterion for the study was regular menstruation (25 - 35 cycle days). The exclusion criteria were: hormonal treatment, use of hormonal contraception, BMI > 25, and history of pregnancy. To assess trunk flexion mobility the finger floor distance test was used. The test was performed on each participant three times: during menstruation (follicular phase), during ovulation (ovulatory phase), and after day 15 of the cycle (luteal phase). Friedman ANOVA was used to determine the effect of the menstrual cycle phases on the finger floor distance test results. It was followed by Wilcoxon signed rank test. Results: There was a significant effect of the phases of the menstrual cycle on the results of the finger floor distance test (p = 0.03). Significantly higher values for the finger floor distance test result in the follicular phase as compared to the ovulatory phase were found (p = 0.02). Conclusions: The comparison of finger floor distance test results obtained in young healthy nulliparas in three phases of the menstrual cycle indicates decreased trunk flexion mobility in the follicular phase.

Relationship between Muscle Flexibility and Characteristics of Muscle Contraction in Healthy Women during Different Menstrual Phases

OBJECTIVE

Skeletal muscle function is vital for preventing injury during exercise. It has been reported that skeletal muscle function fluctuates with the menstrual cycle and is considered one of the causes of injury. This study aimed to clarify the relationship between muscle flexibility and muscle contraction characteristics and their changes with the menstrual cycle.

METHODS

The subjects were healthy women who voluntarily participated in the study through recruitment posters. Muscle flexibility was measured with the passive knee extension (PKE) test, isokinetic knee flexor strength, and the maximum muscle strength exertion angle under two conditions of 60°/s and 120°/s in dominant hamstrings. Additionally, their correlations were analyzed and compared between the menstrual and ovulatory phases.

RESULTS

Sixteen subjects (mean age: 20.56 ± 0.73 years; body mass index: 20.21 ± 1.60) participated in the study. Correlation analysis showed a significant negative correlation between PKE and the maximum muscle strength exertion angle under the condition of 60°/s during the menstrual phase (r = -0.54; p = 0.03). No significant difference was observed in the two-group comparison of the variables measured during the menstrual and ovulatory phases.

CONCLUSION

This study confirmed that the more flexible muscles generate the maximum strength at a more contracted position during the menstrual phase in women. In the future, it is necessary to examine the relationship between the results of this study and exercise performance and injury occurrence.

Menstrual Cycle Changes Joint Laxity in Females—Differences between Eumenorrhea and Oligomenorrhea

The purpose of this study was to investigate the changes in anterior knee laxity (AKL), stiffness, general joint laxity (GJL), and genu recurvatum (GR) during the menstrual cycle in female non-athletes and female athletes with normal and irregular menstrual cycles. Participants were 19 female non-athletes (eumenorrhea, n = 11; oligomenorrhea, n = 8) and 15 female athletes (eumenorrhea, n = 8; oligomenorrhea, n = 7). AKL was measured as the amount of anterior tibial displacement at 67 N–133 N. Stiffness was calculated as change in (Δ)force/Δ anterior displacement. The Beighton method was used to evaluate the GJL. The GR was measured as the maximum angle of passive knee joint extension. AKL, stiffness, GJL, and GR were measured twice in four phases during the menstrual cycle. Stiffness was significantly higher in oligomenorrhea groups than in eumenorrhea groups, although no significant differences between menstrual cycle phases were evident in female non-athletes. GR was significantly higher in the late follicular, ovulation, and luteal phases than in the early follicular phase, although no significant differences between groups were seen in female athletes. Estradiol may affect the stiffness of the periarticular muscles in the knee, suggesting that GR in female athletes may change during the menstrual cycle.

Sexual Dimorphisms in Anterior Cruciate Ligament Injury: A Current Concepts Review

Background:

Although most anterior cruciate ligament (ACL) injuries occur in male athletes, female athletes are consistently observed to be at a higher risk for sports-specific ACL injury.

Purpose:

To provide a thorough review of what is known about the sexual dimorphisms in ACL injury to guide treatment and prevention strategies and future research.

Study Design:

Narrative review.

Methods:

We conducted a comprehensive literature search for ACL-related studies published between January 1982 and September 2017 to identify pertinent studies regarding ACL injury epidemiology, prevention strategies, treatment outcomes, and dimorphisms. By performing a broad ACL injury search, we initially identified 11,453 articles. After applying additional qualifiers, we retained articles if they were published in English after 1980 and focused on sex-specific differences in any of 8 different topics: sex-specific reporting, difference in sports, selective training, hormonal effects, genetics, neuromuscular and kinematic control, anatomic differences, and outcomes.

Results:

A total of 122 articles met the inclusion criteria. In sum, the literature review indicated that female athletes are at significantly higher risk for ACL injuries than are their male counterparts, but the exact reasons for this were not clear. Initial studies focused on intrinsic differences between the sexes, whereas recent studies have shifted to focus on extrinsic factors to explain the increased risk. It is likely both intrinsic and extrinsic factors contribute to this increased risk, but further study is needed. In addition to female patients having an increased risk for ACL injuries, they are less likely than are male patients to undergo reconstructive surgery, and they experience worse postsurgical outcomes. Despite this, reconstructive surgery remains the gold standard when knee stability, return to sports, and high functional outcome scores are the goal, but further research is needed to determine why there is disparity in surgical rates and what surgical techniques optimize postsurgical outcomes for female patients.

Conclusion:

Male athletes often predominated the research concerning ACL injury and treatment, and although sex-specific reporting is progressing, it has historically been deficient. ACL injuries, prevention techniques, and ACL reconstruction require further research to maximize the health potential of at-risk female athletes.

Sensor-Based Indices for the Prediction and Monitoring of Anterior Cruciate Ligament Injury: Reliability Analysis and a Case Study in Basketball

The possibility of measuring predictive factors to discriminate athletes at higher risk of anterior cruciate ligament (ACL) injury still represents an open research question. We performed an observational study with thirteen female basketball players who performed monopodalic jumps and single-leg squat tests. One of them suffered from an ACL injury after the first test session. Data gathered from twelve participants, who did not suffer from ACL injury, were used for a reliability analysis. Parameters related to leg stability, load absorption capability and leg mobility showed good-to-excellent reliability. Path length, root mean square of the acceleration and leg angle with respect to the vertical axis revealed themselves as possible predictive factors to identify athletes at higher risk. Results confirm that six months after reconstruction represents the correct time for these athletes to return to playing. Furthermore, the training of leg mobility and load absorption capability could allow athletes to reduce the probability of new injuries.

Influential Articles on Pediatric and Adolescent Anterior Cruciate Ligament Injuries: A Bibliometric Analysis

BACKGROUND

The understanding of pediatric anterior cruciate ligament (ACL) injuries and optimal treatment has evolved significantly. Influential articles have been previously evaluated using article citations to determine impact.

PURPOSE

To identify and characterize the 50 most cited and recent influential articles relating to pediatric and adolescent ACL injuries, to examine trends in publication characteristics, and to evaluate correlations of study citations with quality of evidence.

STUDY DESIGN

Cross-sectional study.

METHODS

The top 50 most cited articles on pediatric and adolescent ACL injuries were gathered using the Web of Science and Scopus online databases by averaging the number of citations from each database. Articles from recent years were also aggregated and sorted by citation density (citations/year). Publication and study characteristics were recorded. Level of evidence and methodologic quality were assessed where applicable using the modified Coleman Methodology Score (mCMS), modified Jadad scale, and Methodological Index for Non-Randomized Studies (MINORS). Spearman correlation was used to evaluate the association between citation data and level of evidence or methodologic quality scorings.

RESULTS

The top 50 cited papers had a mean of 117.5 ± 58.8 citations (range, 58.5-288.5 citations), with a mean citation density of 9.4 ± 5.4 citations per year (range, 2.9-25.8 citations/year); 80% were published in 2000 or later, and 6% were considered basic science. Articles were mainly level 4 evidence (27/42; 64.3%), and none was level 1. There were moderate, significant associations between publication year and level of evidence (r S = -0.45; P = .0030) and citation density and publication year (r S = 0.59; P < .001). Mean methodologic quality scores were as follows: mCMS, 53 ± 7.2 (range, 39-68); modified Jadad scale, 3.2 ± 1.1 (range, 2-6); and MINORS, 11.2 ± 3.2 (range, 6-20). There was a significant, strong correlation between rank of mean citations and modified Jadad scale (r S = 0.76; P < .0001), suggesting poorer score associated with more mean citations.

CONCLUSION

Influential articles on pediatric and adolescent ACL injuries were relatively recent, with a low proportion of basic science-type articles. Most of the studies had a lower evidence level and poor methodologic quality scores. Higher methodologic quality did not correlate positively with citation data.

Relationship Between Anterior Knee Laxity and General Joint Laxity During the Menstrual Cycle

Background

Anterior cruciate ligament (ACL) injury has been reported to have a higher incidence in women than in men.

Purpose/Hypothesis

The purpose was to examine the relationship of anterior knee laxity (AKL), stiffness, and generalized joint laxity (GJL) with respect to the menstrual cycle. It was hypothesized that AKL and GJL would increase during the ovulation phase, when estrogen levels are high.

Study Design

Descriptive laboratory study.

Methods

A total of 15 female university students aged >20 years and with normal menstrual cycles were evaluated. AKL was measured as anterior tibial displacement of the femur after application of 44-, 89-, and 133-N loads to the tibia. Stiffness was calculated as Δ force/Δ displacement at loads between 44 and 89 N and between 89 and 133 N. The University of Tokyo joint laxity test was used for evaluation of GJL. The participants' menstrual cycle was divided into the early follicular, late follicular, ovulation, and luteal phases using the basal body temperature method and an ovulation kit; AKL and GJL were measured once during each phase. Participants were also stratified according to the presence or absence of genu recurvatum (GR).

Results

There was no significant difference in AKL, stiffness, or GJL among the menstrual phases. In the GR group, AKL values at 89 N and 133 N were significantly higher in the ovulation phase than in the early follicular phase (P = .025 and P =.018, respectively); there were no significant differences in AKL among the phases in the non-GR group. In addition, the GR group in the ovulation phase had significantly higher AKL values at 44 N, 89 N, and 133 N compared with the non-GR group (P = .013, P = .005, and P = .010, respectively). There were no significant differences in GJL among the phases in the GR or non-GR groups.

Conclusion

Women with GR may have increased AKL in the ovulation phase when compared with the early follicular phase, which may be a risk factor for ACL injury.

Clinical Relevance

The results of this study suggest that the ovulation phase may be related to the greater incidence of ACL injuries in women.

The Menstrual Cycle May Affect Anterior Knee Laxity and the Rate of Anterior Cruciate Ligament Rupture: A Systematic Review and Meta-Analysis

BACKGROUND

Women have a higher risk of anterior cruciate ligament (ACL) tears than men, the causes of which are multifactorial. The menstrual cycle and its hormonal effect on the knee may contribute to knee laxity and ACL injury. This work reviewed published studies examining the effects of the phases of the menstrual cycle on anterior knee laxity and the rate of ACL tears.

METHODS

A systematic review with meta-analysis and meta-regression was performed. Studies with data comparing the menstrual cycle phase with ACL injury or anterior knee laxity were included for analysis. Data with regard to patient demographic characteristics, anterior knee laxity, ACL injury, and menstrual cycle phases were extracted from the included studies.

RESULTS

In this study, 1,308 search results yielded 396 articles for review, of which 28 met inclusion criteria. Nineteen studies of knee laxity with 573 combined subjects demonstrated a mean increase in laxity (and standard deviation) of 0.40 ± 0.29 mm in the ovulatory phase compared with the follicular phase and a mean increase in laxity of 0.21 ± 0.21 mm in the luteal phase compared with the follicular phase. Nine studies examining ACL tears with 2,519 combined subjects demonstrated a decreased relative risk (RR) of an ACL tear in the luteal phase compared with the follicular and ovulatory phases combined (RR, 0.72 [95% confidence interval, 0.56 to 0.89]). There were no differences in ACL tear risk between any of the other phases.

CONCLUSIONS

An increased risk of an ACL tear does not appear to be associated with periods of increased laxity in this meta-analysis. Although this suggests that hormonal effects on an ACL tear may not be directly related to increases in knee laxity, the methodologic heterogeneity between published studies limits the conclusions that can be drawn and warrants further investigation.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Sonomechanomyography (SMMG): Mapping of Skeletal Muscle Motion Onset during Contraction Using Ultrafast Ultrasound Imaging and Multiple Motion Sensors

BACKGROUND

Available methods for studying muscle dynamics, including electromyography (EMG), mechanomyography (MMG) and M-mode ultrasound, have limitations in terms of spatial resolution.

METHODS

This study developed a novel method/protocol of two-dimensional mapping of muscle motion onset using ultrafast ultrasound imaging, i.e., sono-mechano-myo-graphy (SMMG). The developed method was compared with the EMG, MMG and force outputs of tibialis anterior (TA) muscle during ankle dorsiflexion at different percentages of maximum voluntary contraction (MVC) force in healthy young adults.

RESULTS

Significant differences between all pairwise comparisons of onsets were identified, except between SMMG and MMG. The EMG onset significantly led SMMG, MMG and force onsets by 40.0 ± 1.7 ms (p < 0.001), 43.1 ± 5.2 ms (p < 0.005) and 73.0 ± 4.5 ms (p < 0.001), respectively. Muscle motion also started earlier at the middle aponeurosis than skin surface and deeper regions when viewed longitudinally (p < 0.001). No significant effect of force level on onset delay was found.

CONCLUSIONS

This study introduced and evaluated a new method/protocol, SMMG, for studying muscle dynamics and demonstrated its feasibility for muscle contraction onset research. This novel technology can potentially provide new insights for future studies of neuromuscular diseases, such as multiple sclerosis and muscular dystrophy.

Ground Reaction Forces Are Predicted with Functional and Clinical Tests in Healthy Collegiate Students

Increased vertical and posterior ground reaction forces (GRFs) are associated with anterior cruciate ligament (ACL) injury. If a practical means to predict these forces existed, ACL injury risk could be attenuated. Forty-two active college-age individuals (21 females, 20.66 ± 1.46 y, 70.70 ± 2.36 cm, 82.20 ± 7.60 kg; 21 males, 21.57 ± 1.28 y, 65.52 ± 1.87 cm, 64.19 ± 9.05 kg) participated in this controlled laboratory study. GRFs were ascertained by having the subjects perform a unilateral landing task onto a force plate. Several clinical measures (Fat Free Mass (FFM), dorsiflexion passive range of motion (DPROM), isometric peak force of the lateral hip rotators, knee flexor/extensor peak force ratio (H:Q), the completion of the overhead deep squat), two functional tests (Margaria–Kalamen, Single Leg Triple Hop (SLTH)), and sex served as the predictor variables. Regression models to predict the GRFs normalized to the FFM (nGRFz, nGRFy) were generated. nGRFz was best predicted with a linear regression equation that included SLTH and DPROM (adjusted R² = 0.274; p = 0.001). nGRFy was best predicted with a linear regression equation that included H:Q, FFM, and DPROM (adjusted R² = 0.476; p < 0.001). Simple clinical measures and functional tests explain a small to moderate amount of the variance associated with the FFM normalized vertical and posterior GRFs in active college-age individuals.

Menstrual cycle variation and gender difference in muscle stiffness of triceps surae

BACKGROUND

We aimed to investigate the menstrual cycle variation and the gender difference of the triceps surae muscle stiffness and passive stiffness of the ankle joint.

METHODS

The subjects of the study included 12 healthy young women and 12 healthy young men. Shear elastic moduli of the lateral gastrocnemius, medial gastrocnemius, and soleus muscles were measured as an index of muscle stiffness using shear wave elastography. The passive stiffness of the ankle joint was calculated from passive torque when the ankle joint was passively dorsiflexed. Measurements were conducted in the follicular, ovulatory, and luteal phases to examine the menstrual cycle variation.

FINDINGS

There was no difference noted in the passive stiffness or triceps surae muscle stiffness for young women in the menstrual cycle. As for gender differences, passive stiffness in all menstrual phases in women was lower while the soleus muscle stiffness in women was higher, compared to that in men.

INTERPRETATION

Our findings suggest that passive stiffness and muscle stiffness did not differ in the menstrual cycle. In addition, the measured part of the soleus was more tensioned in women than in men.

Changes in Knee Laxity and Relaxin Receptor Isoforms Expression (RXFP1/RXFP2) in the Knee throughout Estrous Cycle Phases in Rodents

The changes in knee laxity and relaxin receptor expression at different phases of rodent estrous cycle are not known. Here, changes in the parameter were investigated in rats at different phases of the estrous cycle. Estrous cycle phases of intact female rats were determined by cytological examination of the vaginal smear. Following phase identification, blood was collected for serum hormone analyses. Knee passive range of motion (ROM) was determined by using a digital miniature goniometer. The animals were then sacrificed and patellar tendon, collateral ligaments and hamstring muscles were harvested for relaxin/insulin-like family peptide receptor 1 and 2 (RXFP1/RXFP2) analyses. Knee passive ROM was the highest at proestrus followed by diestrus and the lowest at estrus. Estrogen level was the highest at proestrus while progesterone and relaxin levels were the highest at diestrus. A strong correlation was observed between relaxin and progesterone levels. At proestrus, expression of RXFP1 and RXFP2 proteins and mRNAs were the highest at proestrus followed by diestrus and estrus. The finding shows that higher level of progesterone and relaxin in diestrus might be responsible for higher laxity of knee joint in rats.

Knee Laxity Variations in the Menstrual Cycle in Female Athletes Referred to the Orthopedic Clinic

Background

Anterior cruciate ligament (ACL) rupture is the biggest concern for orthopedic surgeons who are involved in sports injuries, so most of ACL reconstruction surgeries are sports related. ACL injuries in female athletes are 2 - 8 times more common than male athletes in similar sport injuries.

Objectives

The aim of this study was to compare knee laxity changes in the menstrual cycle in female athletes referred to the orthopedic clinic of Imam Khomeini hospital in the north of Iran, Sari, 2013.

Patients and Methods

The present descriptive study was conducted on 40 female athletes that were referred to the orthopedic clinic. Hormone levels, such as estrogen and progesterone were assessed by one laboratory in 3 phases of the menstrual cycle. We used Lachman test and anterior drawer test for knee laxity rate. The descriptive statistics were calculated as indices of central distribution of bonds (x ± SD) and relative frequency distribution was used for qualitative variables.

Results

The results of the current study showed that there is no significant difference in ACL laxity in female athletes in three phases of menstrual cycle; namely menstruation time, ovulation time and mid-luteal phase.

Conclusions

Despite numerous studies and research in the field of knee laxity and effects of female hormones, many researchers do not agree about the effect of female hormones on knee laxity. The current study also reported no relationship between female hormones and knee laxity, while statistics show fundamental difference between male and female athletes.

Jump-landing biomechanics and knee-laxity change across the menstrual cycle in women with anterior cruciate ligament reconstruction

CONTEXT

Of the individuals able to return to sport participation after an anterior cruciate ligament(ACL) injury, up to 25% will experience a second ACL injury. This population may be more sensitive to hormonal fluctuations, which may explain this high rate of second injury.

OBJECTIVE

To examine changes in 3-dimensional hip and knee kinematics and kinetics during a jump landing and to examine knee laxity across the menstrual cycle in women with histories of unilateral noncontact ACL injury.

DESIGN

Controlled laboratory study.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 20 women (age = 19.6 ± 1.3 years, height = 168.6 ± 5.3 cm, mass = 66.2 ± 9.1 kg) with unilateral, noncontact ACL injuries.

INTERVENTION(S)

Participants completed a jump-landing task and knee-laxity assessment 3 to 5 days after the onset of menses and within 3 days of a positive ovulation test.

MAIN OUTCOME MEASURE(S)

Kinematics in the uninjured limb at initial contact with the ground during a jump landing, peak kinematics and kinetics during the loading phase of landing, anterior knee laxity via the KT-1000, peak vertical ground reaction force, and blood hormone concentrations (estradiol-β-17, progesterone, free testosterone).

RESULTS

At ovulation, estradiol-β-17 (t = -2.9, P = .009), progesterone (t = -3.4, P = .003), and anterior knee laxity (t = -2.3, P = .03) increased, and participants presented with greater knee-valgus moment (Z = -2.6, P = .01) and femoral internal rotation (t = -2.1, P = .047). However, during the menses test session, participants landed harder (greater peak vertical ground reaction force; t = 2.2, P = .04), with the tibia internally rotated at initial contact (t = 2.8, P = .01) and greater hip internal-rotation moment (Z = -2.4, P = .02). No other changes were observed across the menstrual cycle.

CONCLUSIONS

Knee and hip mechanics in both phases of the menstrual cycle represented a greater potential risk of ACL loading. Observed changes in landing mechanics may explain why the risk of second ACL injury is elevated in this population.

Accuracy of calendar-based methods for assigning menstrual cycle phase in women

Background:

Sex steroid hormone fluctuations during the menstrual cycle are considered a risk factor for noncontact anterior cruciate ligament injuries.

Objective:

To determine whether self-reported menstrual history data can be used to accurately categorize menstrual cycle events using calendar-based counting methods.

Study Design:

Descriptive laboratory study.

Methods:

Seventy-three women completed a menstrual history questionnaire and submitted to blood sampling for the first 6 days of menses and 8 to 10 days after a positive ovulation test over 2 consecutive months. Frequency counts determined whether appropriate criterion hormone (progesterone) levels were achieved at predefined calendar days.

Results:

For the criterion of progesterone >2 ng/mL, 18% and 59% of women attained it when counting forward 10 to 14 days after the onset of menses and counting back 12 to 14 days from the end of the cycle, respectively. Most women (76%) attained the criterion for ovulation 1 to 3 days after a positive urinary ovulation test. Regardless of the counting method employed, the criterion of progesterone >4.5 ng/mL for identifying midluteal phase was attained in 67% of cases. Serial blood sampling for 3 to 5 days after the positive urinary ovulation test captured 68% to 81% of the hormone values indicative of ovulation and 58% to 75% indicative of the luteal phase.

Conclusion:

These data suggest that self-reported menstrual history and calendar-based counting methods should not be used alone if accurate identification of ovulation is essential. A urinary ovulation test and serial blood samples for verification of progesterone postovulation enhance the proper identification of menstrual cycle events.

Clinical Relevance:

Given the cost of serial blood sampling on numerous days, the use of urinary ovulation kits and strategically selected serial blood sampling could significantly reduce participant burden and provide cost-effective measures for clinical studies related to anterior cruciate ligament injury epidemiology.

Effect of functional lumbar stabilization exercises on pain, disability, and kinesiophobia in women with menstrual low back pain: a preliminary trial

OBJECTIVE

The purpose of this preliminary study was to investigate the effect of functional lumbar stabilization exercises on pain, disability, and kinesiophobia in women with menstrual low back pain (LBP).

METHODS

Thirty women with menstrual LBP participated in the study. Subjects were assigned to a control group (n = 10, mean age = 25.1 ± 4.7 years) and an intervention group (n = 20, mean age = 21.7±2.4 years). Treatment for the intervention group consisted of functional lumbar stabilization exercises, 10 repetitions each, 3 times a day, for 3 consecutive months. The women in the control group received no exercise and performed their regular activity daily living. Pain intensity using a Numeric Pain Scale (NPS), Oswestry Disability Index (ODI), Roland-Morris Questionnaire (RMQ), and Tampa Scale of Kinesiophobia (TSK) was collected at baseline and at the end of 3 months in both groups.

RESULTS

Statistical analysis (paired t test) revealed a significant decrease in NPS, ODI, RMQ, and TSK after treatment in the intervention group. No significant difference in NPS, ODI, RMQ, or TSK was found between pre- and postmeasurement scores in the control group. In the analysis of covariance, controlling for pretest scores, a significant difference was found between the 2 groups in the postmeasurement score of NPS (P = .01), ODI (P < .001), RMQ (P = .002), and TSK (P = .04).

CONCLUSION

Lumbar stabilization exercises were shown to improve pain, disability, and kinesiophobia during menstrual LBP for subjects who participated in this preliminary study compared to those who did not receive the intervention.

Anterior cruciate ligament elasticity and force for flexion during the menstrual cycle

Background

A high occurrence of knee injuries have been observed in women during the menstrual cycle (MC). As a result, numerous studies have been conducted regarding knee ligament elasticity during the MC. Some researchers believe that since estrogen receptor b 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. 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 knee laxity.

Material/Methods

Ten non-athletic young healthy females, 18 to 30 years of age participated in the study. E2 serum concentrations, anterior cruciate ligament (ACL) elasticity, and force to flex the knee (FFK), knee flexion-extension hysteresis (KFEH) were assessed both at ambient temperature (22°C) and after 38°C warming. Testing was performed multiple times during the participant’s MC, for one full MC.

Results

ACL elasticity was significantly higher (P<0.01) and FFK and KFEH were significantly lower (p<0.05) during ovulation when E2 levels were highest. ACL elasticity was still higher during ovulation after warming to 38°C. But, the effects of MC on FFK and KFEH were reduced by tissue warming.

Conclusions

ACL elasticity, FFK, and KFEH was affected not only by E2 but also tissue temperature. However, E2 had more impact on ACL elasticity while tissue temperature had more impact on FFK and KFEH at 38°C warming.

Anterior cruciate ligament tear during the menstrual cycle in female recreational skiers

INTRODUCTION

Women run a 4-8-fold greater risk of anterior cruciate ligament (ACL) tear than men, and especially during the pre-ovulation stage of their cycle. The main study objective was to describe the distribution of ACL lesions according to menstrual cycle in a large population of female recreational skiers.

MATERIALS AND METHODS

A prospective study was conducted during the 2010-11 ski season on women sustaining ACL tear during skiing. Patients filled out a questionnaire during consultation with the mountain physician, including date of last menstrual period (LMP) and contraceptive method. Fifty-seven of the 229 patients with diagnosed ACL tear were excluded from analysis, 41 being post-menopausal (mean age, 47 ± 9 years), and 16 having irregular cycles or LMP>30 days. One hundred and seventy-two patients (mean age, 34 ± 8.7 years) were thus included.

RESULTS

Fifty-eight women (33.72%) were in follicular phase, 63 (36.63%) in ovulatory phase and 51 (29.65%) in luteal phase; difference with respect to the theoretic distribution regardless of menstrual phase was highly significant: χ(2)=48.32; P=0.00001. Fifty-three of the 172 women (30.8%) were taking oral contraceptives. ACL tear was 2.4-fold more frequent in pre-ovulatory than post-ovulatory phase, whether in women using oral or other contraceptives: 85/119 (71.4%) vs. 36/53 (67.9%); P=0.64.

CONCLUSION

ACL tear risk in skiing in women is not constant over the menstrual cycle, being 2.4-fold more frequent in pre-ovulatory (follicular and ovulatory) than post-ovulatory phase (luteal). Oral contraception seems not to exert any protective effect.

LEVEL OF EVIDENCE

Level IV. Retrospective cohort study.

Influência das diferentes fases do ciclo menstrual na flexibilidade de mulheres jovens

INTRODUÇÃO: O ciclo menstrual é o principal responsável por modificações da fisiologia feminina, que pode afetar algumas respostas morfofuncionais. OBJETIVO: Verificar a influência das diferentes fases do ciclo menstrual na flexibilidade de mulheres jovens. MÉTODO: 44 voluntárias divididas em um grupo controle (n = 24), que fazia uso regular de contraceptivos hormonais, e um grupo experimental (n = 20), que não utilizava anticoncepcionais, foram submetidas a três dias de avaliações, uma em cada fase do ciclo menstrual (folicular, ovulatória e lútea). Foram avaliados dados antropométricos (massa corporal, índice de massa corporal, circunferência de cintura e abdômen) e de composição corporal (percentual de gordura e massa magra). A flexibilidade foi mensurada através do teste de sentar e alcançar no banco de Wells. Aplicou-se, então, o teste não paramétrico de Mann-Whitney para as comparações intergrupos e o teste de Friedman para a comparação entre as diferentes fases menstruais. Resultados: Não foram encontradas diferenças significativas intra e intergrupos entre as diferentes fases do ciclo (p > 0,05). Foi observada maior variabilidade no grupo controle em comparação ao experimental. CONCLUSÃO: As diferentes fases do ciclo menstrual não interferem na flexibilidade de mulheres jovens, independente do uso de anticoncepcionais hormonais.

The effects of oral contraceptive use on muscle stiffness across the menstrual cycle

OBJECTIVE

To determine the effect of oral contraceptives (OC) on hamstring neuromechanics and lower extremity stiffness across the menstrual cycle (MC).

DESIGN

Causal comparative.

SETTING

Research laboratory.

PARTICIPANTS

Thirty, healthy, normally menstruating female volunteers who were using OC (OC group, n = 15) or not (non-OC group, n = 15).

ASSESSMENT OF RISK FACTORS

Stiffness and hamstring neuromechanics were assessed at 2 points of the MC corresponding to low (menses) and high (ovulation) hormone concentrations. Menses testing took place 3 to 5 days after the onset of menses (or pills 3-5 for the OC group). Ovulation test session occurred 2 to 4 days after ovulation identified using a commercial ovulation kit (or pills 15-17 in the OC group).

MAIN OUTCOME MEASURES

Lower extremity stiffness and hamstring neuromechanics [stiffness, electromechanical delay, rate of force production (RFP), time to 50% peak force (T50%)] and blood plasma concentrations of estradiol-β-17, free testosterone, and progesterone.

RESULTS

Estradiol-β-17, free testosterone, and progesterone increased at ovulation in the non-OC group and remained constant in the OC group. No changes were observed across the MC or between the groups in other variables (P > 0.05).

CONCLUSIONS

Although previous literature suggests a prophylactic effect of OC use with respect to musculoskeletal injury risk, our results indicate that OC use does not affect muscle properties in manners thought to reduce ACL injury risk.

Anterior and posterior knee laxity in a young adult Korean population

PURPOSE

The purposes of this study were (1) to determine normal anterior and posterior knee laxity in a healthy young adult (20-30 years old) Korean population, (2) to compare knee laxity between the male and female populations, (3) to investigate whether generalized joint laxity affects anterior and posterior knee laxity, (4) to determine side-side differences between right and left knees, and thus, to determine normal values of side-side differences.

METHODS

Normal values of anterior and posterior knee laxity were measured in 100 healthy volunteers (50 men and 50 women) aged between 20 and 30 years. Stress radiography using a Telos device was performed in 20 and 70° of knee flexion for 134N anterior and posterior loads. Anterior and posterior tibial displacements relative to the femur condyle were measured using a computerized system.

RESULTS

In the 100 subjects (200 knees), anterior knee laxity was greater at 20° of flexion with a mean of 4.9 ± 2.3 mm (P < 0.05) and posterior knee laxity was greater at 70° of flexion with a mean of 4.6 ± 2.7 mm (P < 0.05). The mean side-side difference was 1.4 ± 0.9 mm (range, -3 to +3). Women had greater anterior laxity (P < 0.05) than men at both 20 and 70° of flexion, but posterior laxity was not different (ns). Generalized joint laxity was greater in women compared to men (P < 0.05). Subjects with generalized joint laxity had greater laxity than normal populations in both 20 and 70° of flexion (P < 0.05). Side-side differences between right and left knees were not significantly different in women and men or between subjects with normal and generalized joint laxity (ns).

CONCLUSIONS

This study suggests that the Korean population exhibits a wide range of normal anterior and posterior knee laxity, but small side-side differences. Subjects with generalized laxity showed greater knee laxity than those without, but side-side differences were less than 3 mm in all subjects. Thus, clinical guideline that a side-side difference more than 3 mm of anterior knee laxity is abnormal can be applicable for the subjects with generalized laxity.

The female athlete

Over time, women have become more extensively involved in athletic programs. The female athlete presents a unique challenge to sports medicine in general. Although specific types of injuries are the same as in the male athlete, the female athlete is at higher risk for some of these injuries. Injuries may be sport specific, but gender-related injuries are also related to morphologic and physiologic differences between the male and female athlete. This article reviews some of the differences between the male and female athlete and focuses on a few prominent injuries or risks related specifically to the woman athlete.

A comparison of cyclic variations in anterior knee laxity, genu recurvatum, and general joint laxity across the menstrual cycle

Changes in anterior knee laxity (AKL), genu recurvatum (GR) and general joint laxity (GJL) were quantified across days of the early follicular and early luteal phases of the menstrual cycle in 66 females, and the similarity in their pattern of cyclic variations examined. Laxity was measured on each of the first 6 days of menses (M1-M6) and the first 8 days following ovulation (L1-L8) over two cycles. The largest mean differences were observed between L5 and L8 for AKL (0.32 mm), and between L5 and M1 for GR (0.56°) and GJL (0.26) (p < 0.013). At the individual level, mean absolute cyclic changes in AKL (1.8 ± 0.7 mm, 1.6 ± 0.7 mm), GR (2.8 ± 1.0°, 2.4 ± 1.0°), and GJL (1.1 ± 1.1, 0.7 ± 1.0) were more apparent, with minimum, maximum and delta values being quite consistent from month to month (ICC(2,3) = 0.51-0.98). Although the average daily pattern of change in laxity was quite similar between variables (Spearman correlation range 0.61 and 0.90), correlations between laxity measures at the individual level were much lower (range -0.07 to 0.43). Substantial, similar, and reproducible cyclic changes in AKL, GR, and GJL were observed across the menstrual cycle, with the magnitude and pattern of cyclic changes varying considerably among females.

Tibial acceleration variability during consecutive gait cycles is influenced by the menstrual cycle

BACKGROUND

The relationship between the phases of the menstrual cycle and injury risk remains unclear. Neuromuscular function may be compromised during menstruation, which could result in reduced cyclicality of movement patterns. We hypothesize that mediolateral (varus/valgus) knee acceleration during running gait will possess increased variability during menstruation when compared to approximately ovulation in women who do not take the monophasic oral contraceptive pill (MOCP).

METHODS

Thirty-six women (18 MOCP users: MOCP group and 18 non-pill users: NP group) performed six-minute treadmill running trials at 10 km h(-1) with an accelerometer fixed to the proximal tibia. Trials were performed at menstruation and approximately equal ovulation (for the MOCP group at a similar stage of the cycle) in a randomized order. The cyclicality of gross mediolateral tibial acceleration during 15 consecutive strides was assessed using combined wavelet and autocorrelation analysis. Longitudinal and anteroposterior accelerations were also examined. Repeated measures analysis of variance (ANOVA) tests were performed to assess differences at each stage of the menstrual cycle (alpha=0.05).

FINDINGS

Gross mediolateral acceleration in the NP group had significantly (P=0.022) increased variability at the time of menstruation compared to approximately equal ovulation, and was also significantly (P=0.011) more variable than the MOCP group at the corresponding time point. No significant difference was observed for any measure in the MOCP group.

INTERPRETATION

Increased variability in the NP users at menstruation may be a result of compromised motor control strategies. This provides further evidence of variability in performance and motor control during menstruation, and may have implications for a female athlete's risk of injury.

Correlates of knee anterior laxity in sportswomen

The purpose of this study was to evaluate whether any of the following factors are related to knee anterior laxity in healthy sportswomen: anthropometric characteristics, lower limb alignment characteristics, hormone-related factors and sport history. Six hundred and sixteen sportswomen were tested in the pre-season. The data have been analysed using linear regression for possible association of knee anterior laxity with other variables. Univariate linear regression indicated a positive association of knee anterior laxity with knee extension and navicular drop and a negative association with body height. Multivariate linear regression analysis showed statistically significant associations between knee anterior laxity and the combination of passive knee extension and the chosen sport (R(2)=0.089; p<0.05). The combination of passive knee extension and sport type was found to be related to the amount of knee anterior laxity, although the association was weak with this combination of factors able to explain only about 9% of the variability in laxity. Knowing which factors influence the amount of knee anterior laxity will help us to better interpret the results of knee anterior laxity testing and help us to understand the possible role of knee anterior laxity as a risk factor for knee injury.

Menstrual cycle variations in oestradiol and progesterone have no impact on in vivo medial gastrocnemius tendon mechanical properties

BACKGROUND

Tendon tissue contains oestrogen receptors and is therefore likely to be responsive to female sex hormones. Here we examine any effect of levels of female sex hormones associated with the menstrual cycle phase on corresponding tendon mechanical properties.

METHODS

Fifteen healthy females aged 23 (SEM 1.0 years) underwent three assessments of medial gastrocnemius tendon mechanical properties. Assessments were carried out once during days 1-4, 12-14 and 20-23 (with day 1 being the first day of menstruation). Venous blood samples were taken on the same days as tendon properties assessments to quantify serum levels of oestradiol and progesterone.

FINDINGS

There was no significant difference in the stiffness of the medial gastrocnemius tendon over the course of the menstrual cycle (days 1-4, 65.08 (SEM 5.16 Nm m(-1)), days 12-14, 62.73 (SEM 5.82 Nm m(-1)), days 20-23, 66.74 (SEM 7.14 Nm m(-1))). There were also no significant differences in tendon length and cross-sectional area which led to no significant differences in Young's modulus values. No correlations were found between serum levels of oestradiol and/or progesterone and tendon stiffness and/or Young's modulus.

INTERPRETATION

Acute fluctuations in female sex hormones have no significant effect on medial gastrocnemius tendon mechanical properties. In a context where studies are often limited to selecting only oral contraceptive-users as participants in order to minimise potential noise related to the anticipated effects of menstrual cycle hormones on physical performance, our findings provide the basis for enabling the pooling of female tendon data, regardless of the phase of the menstrual cycle of individual participant.

Does gender influence neuromotor control of the knee and hip?

Patellofemoral pain (PFP) is a common condition that occurs more frequently in females. Anatomical, hormonal and neuromuscular factors have been proposed to contribute to the increased incidence of PFP in females, with neuromuscular factors considered to be of particular importance. This cross-sectional study aimed to evaluate differences in the neuromotor control of the knee and hip muscles between genders and to investigate whether clinical measures of hip rotation range and strength were associated with EMG measures of hip and thigh motor control. Twenty-nine (16 female and 13 male) asymptomatic participants completed a visual choice reaction-time stair stepping task. EMG activity was recorded from vastus medialis oblique, vastus lateralis, anterior and posterior gluteus medius muscles. In addition hip rotation range of motion and hip external rotation, abduction and trunk strength were assessed. There were no differences in the timing or peak of EMG activation of the vasti or gluteus medius muscle between genders during the stepping task. There were however significant associations between EMG measures of motor control of the vasti and hip strength in both females and males. These findings are suggestive of a link between hip muscle control and vasti neuromotor control.

Changing hormone levels during the menstrual cycle affect knee laxity and stiffness in healthy female subjects

BACKGROUND

Whether knee laxity varies throughout the menstrual cycle remains controversial. As increased laxity may be a risk factor for anterior cruciate ligament (ACL) injury, further research is warranted.

HYPOTHESIS

Variation in estradiol and progesterone levels during the menstrual cycle influences knee laxity and stiffness.

STUDY DESIGN

Case control study; Level of evidence, 3.

METHODS

The serum estradiol and progesterone levels of 26 healthy female subjects were recorded in the follicular phase, ovulation, and the luteal phase. Knee joint laxity was assessed using a standard knee arthrometer at the same intervals. Stiffness changes in the load-displacement curve were determined. Hormone levels across the cycle were compared between responders and nonresponders, defined by whether changes in knee laxity at 89 N occurred.

RESULTS

Greater laxity at 89 N during ovulation was observed (ovulation: 5.13 +/- 1.70 mm vs luteal: 4.55 +/- 1.54 mm, P = .012). In knee laxity testing at manual maximum load, greater laxity was noticed during ovulation (14.43 +/- 2.60 mm, P = .018), as compared with the follicular phase (13.35 +/- 2.53 mm). A reduction in knee stiffness of approximately 17% (ovulation: 12.48 +/- 5.46 N/mm vs luteal: 15.02 +/- 7.71 N/mm, P = .042) during ovulation was observed. However, there were no differences in hormone levels between responders and nonresponders at 89 N.

CONCLUSION

Female hormone levels are related to increased knee joint laxity and decreased stiffness at ovulation. To understand subject variations in knee joint laxity during the menstrual cycle in female athletes, further investigation is warranted.

The interrelationships among sex hormone concentrations, motoneuron excitability, and anterior tibial displacement in women and men

CONTEXT

Sex hormone fluctuations have been implicated as a contributing factor to the high rates of noncontact injury to the anterior cruciate ligament in females.

OBJECTIVE

To determine the strength of the relationships among variables of sex hormone concentrations, motoneuron excitability, and anterior tibial displacement (ATD) in women and men and to determine if these relationships differ between the sexes.

DESIGN

Cohort study.

SETTING

Sports medicine laboratory.

PATIENTS OR OTHER PARTICIPANTS

Twenty-eight regularly menstruating women (age = 22.4 +/- 3.4 years) and 15 men (age = 22.3 +/- 3.7 years) participated in the study.

INTERVENTION(S)

Fluctuations in sex hormones were determined for the participants. Female participants were tested every other day of their menstrual cycles, whereas male participants were tested every fourth day during the 28-day period.

MAIN OUTCOME MEASURE(S)

We measured Hoffmann reflexes (maximum Hoffmann reflex [H(max)] to maximum M-wave [M(max)] ratio in the soleus), ATD under a 134-N load, and saliva concentrations of estrogen and progesterone. The independent variable was sex. Pearson product moment correlation coefficients were calculated for each participant by pairing measurements made on the same day. Two-tailed independent-samples t tests were used to determine the difference between the male and female correlations for each variable.

RESULTS

Over the course of the study, the relationships between H(max)ratioM(max) and estrogen, H(max)ratioM(max) and progesterone, ATD and estrogen, and ATD and progesterone were not different between the sexes. However, the relationship between ATD and progesterone was different between the sexes (P = .036).

CONCLUSIONS

The observed correlations did not support our hypothesis that the relationships between sex hormone levels and reflex activity or between sex hormone levels and ATD would be different for women compared with men. If sex hormone concentrations significantly contribute to anterior cruciate ligament ruptures because of changes in laxity or in motoneuron excitability, their mechanism of action is likely multifactorial and complex.

Effects of estrogen on the mechanical behavior of the human Achilles tendon in vivo

The purpose of this study was to elucidate the effect of normal fluctuating [non-monophasic oral contraceptive pill (MOCP) users] and low, consistent (MOCP users) endogenous plasma estrogen levels on the strain behavior of the Achilles tendon in vivo. Twenty women (age 28.0 +/- 4.2 yr, height 1.67 +/- 0.07 m, mass 61.6 +/- 6.8 kg) who had been using the MOCP for at least 12 mo together with 20 matched women who were non-MOCP users (age 31.9 +/- 7.3 yr, height 1.63 +/- 0.05 m, mass 62.5 +/- 5.9 kg) participated in this study. Non-MOCP users were tested at the time of lowest (menstruation) and highest (approximately same as ovulation) estrogen, whereas MOCP users, who exhibited constant and attenuated endogenous estrogen levels, were tested at day 1 and day 14 of their cycle. At each test session, maximal isometric plantarflexion efforts were performed on a calf-raise apparatus while synchronous real-time ultrasonography of the triceps surae aponeurosis was recorded. Achilles tendon strain (%) was calculated by dividing tendon displacement during plantarflexion by resting tendon length. Repeated-measures ANOVA revealed a significant (P < 0.05) main effect of subject group with significantly lower Achilles strain (25.5%) in the MOCP users compared with the non-MOCP users. In conclusion, acute fluctuations in plasma estrogen across the menstrual cycle in non-MOCP users did not alter the strain behavior of the Achilles tendon. Conversely, long-term exposure to attenuated estrogen in MOCP users resulted in a decrease in Achilles tendon strain, which is thought to be attributed to the effects of endogenous estrogen on collagen synthesis. These findings have a number of important functional and clinical implications.

Relationship of the menstrual cycle phase to anterior cruciate ligament injuries in teenaged female athletes

INTRODUCTION

Anterior cruciate ligament (ACL) injuries are more common among female athletes compared to male athletes. Several studies have been reported to explain the gender difference in ACL injury rates and several risk factors underlying gender disparity are believed to exist. Hormonal effects are considered to be one of the etiological factors for female non-contact ACL injuries. The objectives of this study were to determine if ACL injuries occurred randomly or correlated with a specific phase of the female menstrual cycle in teenaged female athletes and then to determine if pre-menstrual and menstrual dysfunctions influenced these ACL injuries.

MATERIALS AND METHODS

Eighteen of 37 consecutive female athletes, with ACL injuries, met the study criteria: teenage, with regular menstrual cycle, and non-contact injury. The menstrual history, athletic activity, and injury history were collected.

RESULTS

Seventy-two percent of the subjects had premenstrual symptoms and 83% had menstrual symptoms. The subjective activity level at the follicular phase was significantly lowest between the phases. A significant statistical association was found between the phase of the menstrual cycle and ACL injuries (P = 0.0002). There were more injuries in the ovulatory phase than expected, and fewer injuries occurred in the other phases.

CONCLUSION

The results showed a significant increase in non-contact ACL injuries in teenage female athletes during the ovulatory phase of the menstrual cycle and the subjective activity level and the premenstrual and menstrual symptoms might not affect the likelihood of the injuries. These findings suggest that sex hormones might play a role in the incidence of female non-contact ACL injuries.

Knee-laxity measurements examined by a left-hand- and a right-hand-dominant physiotherapist, in patients with anterior cruciate ligament injuries and healthy controls

The purpose of the study was to analyse and compare KT-1000 knee laxity as examined by a left-hand- and a right-hand-dominant physiotherapist in a group of patients with an anterior cruciate ligament (ACL) injury and a group of patients, 2 years after ACL reconstruction. The other aim was to measure and analyse knee laxity in a group of persons without any known knee problems. A cross-sectional examination of two groups of patients pre-operatively and post-operatively after ACL reconstruction and examination of healthy controls on two different occasions was performed. Fifty-three patients who were scheduled for ACL reconstruction and 39 patients who attended a 2-year follow-up examination were included in the study. In the ACL-deficient group, 32 patients had a right-sided ACL injury and 21 patients a left-sided ACL injury. The corresponding figures in the post-operative group were 21 patients with a right-sided ACL injury and 18 patients with a left-sided ACL injury. Twenty-eight healthy persons without any known knee problems served as controls. One left-hand- and one right-hand-dominant experienced physiotherapist performed all the examinations. To be able to evaluate the intra and inter-reliability of the examiners the controls were examined at two occasions. The left-hand-dominant physiotherapist measured significantly higher absolute laxity values in the left knee, both injured and non-injured ones, compared with the right-hand-dominant physiotherapist. This was found irrespectively of whether the patients belonged to the ACL deficient or the post-operative group. In the healthy control group, the right-hand-dominant physiotherapist measured significantly higher knee-laxity values in the right knee compared with the left-hand-dominant physiotherapist. Correspondingly, the left-hand-dominant physiotherapist measured significantly higher knee laxity values in the left knee. We conclude that KT-1000 arthrometer laxity measurements can be affected by the hand dominance of the examiner. This might affect the reliability of KT-1000 arthrometer measurements. Level of evidence is II.

ACL Tears in Female Athletes

With the growing number of female athletes, an increase is occurring in the number of sports-related injuries, which can cause physical, psychological, academic, and financial suffering. Female athletes are reported to be two to eight times more likely to sustain an anterior cruciate ligament (ACL) injury than male athletes. Further research on risk factors and preventative strategies for the female ACL is needed, because the cause of the disparity in injury rates remains equivocal and controversial. Individualized treatment for the injured knee is necessary and can include either conservative treatment or reconstructive surgery.

Effect of habitual exercise on the structural and mechanical properties of human tendon, in vivo, in men and women

We examined whether long-term habitual training (a) was associated with differences in structural and mechanical properties in tendon in women and (b) yielded different tendon properties in men and women. Ten male runners, 10 female runners and 10 female non-runners were tested. Tendon cross-sectional area (CSA) and length of the patellar and Achilles tendon were determined with MRI. Ultrasonography-based measurement of tendon elongation and force during isometric contractions provided mechanical properties. Distal patellar and Achilles tendon CSAs were greater than the proximal part in all three groups (P<0.05). Weight-normalized Achilles tendon CSA were similar in trained (2.78+/-0.17 mm(2)/kg(3/4)) and untrained women (2.60+/-0.13 mm(2)/kg(3/4)), while that in trained men (3.77+/-0.27 mm(2)/kg(3/4)) was greater compared with trained women (P<0.01). Patellar tendon CSA were comparable in trained and untrained women, while that in trained men was greater compared with trained women (P<0.01). Patellar tendon stiffness was greater in male runners (3528+/-773 N/mm) compared with female runners (2069+/-666 N/mm) and non-runners (2477+/-381 N/mm), (P<0.01), but patellar tendon deformation, stress, strain and modulus were similar. These data indirectly suggest that the ability of Achilles and patellar tendons to adapt in response to habitual loading such as running is attenuated in women.

Reproductive hormone effects on strength of the rat anterior cruciate ligament

The material properties of the anterior cruciate ligament (ACL) in female rats with normal estrous cycles were compared to those regulated by oral contraceptive steroids. Forty female Sprague-Dawley rats were divided into two groups: an experimental group received daily ethinylestradiol and levonorgestrel in a dosing model designed to simulate a typical oral contraception regime in humans, while a control group received daily oral placebo. After eight cycles, six rats from each group underwent daily phlebotomy to measure serum estradiol and progesterone levels over the course of a single 5-day estrous cycle. Significant differences between groups were found for the area under the curve of blood progesterone levels versus time over the length of the estrous cycle (P=0.02). After 12 cycles, the rats were euthanized and one femur-ACL-tibia complex from each animal was dynamically loaded to failure. The ACLs from the rats in the experimental group had significantly decreased average and tangent stiffness, (P=0.002 and 0.0001, respectively), and significantly increased elongation (P=0.002) and total energy absorbed (P=0.03), or greater toughness than controls. In rats, it appears that the administration of reproductive hormones designed to simulate typical oral contraception in humans alters the mechanical properties of the rat ACL.

Effects of the menstrual cycle on anterior cruciate ligament injury risk: a systematic review

Several theories have been proposed to explain the 3- to 6-fold gender difference in the incidence of anterior cruciate ligament injuries. One potential theory for the increased incidence is based on gender-related hormonal differences between men and women, especially after puberty and the onset of menses in the female athlete. The purpose of this systematic review was to compile and systematically analyze the published literature to determine if the menstrual cycle is associated with anterior cruciate ligament injury risk and to provide an objective comparison of the published results. Investigations were included in the systematic review if the report included associations between the menstrual cycle and noncontact anterior cruciate ligament injuries in female athletes. Abstracts and unpublished studies were excluded. Seven articles were identified that met the systematic review inclusion criteria. The 7 reviewed studies favored an effect of the first half, or preovulatory phase, of the menstrual cycle for increased anterior cruciate ligament injuries. The 6 studies that separated the non-oral contraceptive and oral contraceptive data also favored an effect of the first half of the menstrual cycle for increased anterior cruciate ligament injuries. The clinical relevance of this finding is that female athletes may be more predisposed to anterior cruciate ligament injuries during the preovulatory phase of the menstrual cycle. These findings may lead to potential interventions targeted toward this phase of the menstrual cycle to reduce the incidence of anterior cruciate ligament injury.

Effects of menstrual-cycle hormone fluctuations on musculotendinous stiffness and knee joint laxity

The high risk of anterior cruciate ligament (ACL) injuries in female athletes may be related to hormonal fluctuations resulting in an increased laxity of ligaments and muscles. This study examined changes in lower limb musculotendinous stiffness (MTS) and knee laxity over the course of the menstrual cycle and investigated the interaction of warm-up on MTS. Eleven female netball players aged 16-18 years who were not using hormonal contraceptives and demonstrated regular menstrual cycles participated in this study. Test-sessions were conducted at onset of menses, mid-follicular phase, ovulation and mid-luteal phase. ACL laxity was determined at each test-session using a KT2000 knee arthrometer. MTS was assessed prior to, and following a standardised warm-up. Repeated measures ANOVA revealed significant (P < 0.05) main effects of test-session and warm-up on MTS. MTS was found to significantly decrease by 4.2% following the warm-up intervention. MTS was significantly lower at week 3 (ovulatory phase) in contrast to weeks 1 and 2 (8.7 and 4.5%, respectively). For knee laxity measures, repeated measures ANOVA revealed no significant (P < 0.05) differences across the menstrual cycle. A reduction in MTS results in greater reliance on reflexive response from the contractile components of the muscle due to a decreased contribution from passive elastic structures and will also increase electromechanical delay. Given that extreme loads are applied to the knee joint within milliseconds, the contractile components cannot respond quickly enough to counteract these sudden and potentially damaging forces. These effects are augmented following a moderate warm-up. Oestrogen fluctuations had no significant effect on anterior knee laxity, however, the effects on MTS over the 28-day cycle were considerable. Future studies should use matched subjects who are using the monophasic oral contraceptive pill to investigate the effects of oestrogen supplementation on lower limb MTS.

The effects of the menstrual cycle on anterior knee laxity: a systematic review

Female athletes are at a 4- to 6-fold increased risk of anterior cruciate ligament (ACL) injury compared with male athletes. There are several medical, emotional and financial burdens associated with these injuries. Sex hormones may be involved in the ACL injury disparity, with potential associations reported between phases of the menstrual cycle and ACL injury rates. The reported relationships between ACL injury and menstrual status may be related to associated changes in ligament mechanical properties from cyclic fluctuations of female sex hormones. A PubMed electronic database literature search, including MEDLINE (1966-2005) and CINAHL (1982-2005), with the search terms 'menstrual cycle' and 'knee laxity' was used for this systematic review. Studies were included in this systematic review if they were prospective cohort studies and investigated the association between the menstrual cycle and anterior knee laxity in females. Nine prospective cohort studies, published as 11 articles, were included in the systematic review. Six of nine studies reported no significant effect of the menstrual cycle on anterior knee laxity in women. Three studies observed significant associations between the menstrual cycle and anterior knee laxity. These studies all reported the finding that laxity increased during the ovulatory or post-ovulatory phases of the cycle. A meta-analysis, which included data from all nine reviewed studies, corroborated this significant effect of cycle phase on knee laxity (F-value = 56.59, p = 0.0001). In the analyses, the knee laxity data measured at 10-14 days was >15-28 days which was >1-9 days. Future studies testing the relationship between the menstrual cycle and potentially associated parameters should consider the limitations outlined in this article and control for potential biases and confounders. Power analyses should be utilised. Subjects should be randomly entered into the studies at alternate points in the cycle, and standard and consistent data acquisition and reporting methods should be utilised. Future studies should clearly define what constitutes a 'normal' cycle and appropriate control subjects should be utilised. Furthermore, there is a need to define cycle phase (and timing within cycle phase) with actual hormone levels rather than a day of the cycle. Although hormone confirmations were provided in many of the studies that selected specific days to depict a particular cycle for all women, it is unknown from these data if they truly captured times of peak hormone values in all women. A combined systematic review and meta-analysis of the literature indicate that the menstrual cycle may have an effect on anterior-posterior laxity of the knee; however, further investigation is needed to confirm or reject this hypothesis.

The effects of estrogen on material and mechanical properties of the intra- and extra-articular knee structures

BACKGROUND

Female athletes have a higher incidence of anterior cruciate ligament injuries than do male athletes in similar sports. Hormones, particularly estrogen, have been indicated by some studies to be correlated with the disproportionate number of anterior cruciate ligament injuries in female athletes.

HYPOTHESIS

Estrogen does not affect the mechanical or material properties of primate anterior cruciate ligaments or patellar tendons.

STUDY DESIGN

Controlled laboratory study.

METHODS

Twenty-six cynomolgus monkeys (Macaca fascicularis) were divided into 2 groups: sham operated (estrogen maintained, n = 12) and ovariectomized (estrogen deficient, n = 14). After 2 years, the animals were sacrificed, and various properties of ligaments were tested. Two different ligaments were studied, the anterior cruciate ligament and patellar tendon.

RESULTS

No differences were found between the sham-operated (sham) and ovariectomized group for failure load (anterior cruciate ligament: sham, 394 +/- 67 N; ovariectomized, 392 +/- 96 N; P > .74), stiffness, elongation at failure, ultimate stress (anterior cruciate ligament: sham, 115 +/- 30 MPa; ovariectomized, 128 +/- 36 MPa; P > .58), ultimate strain, modulus, failure sites, or energy to failure.

CONCLUSION

Endogenous estrogen does not directly affect the mechanical or material properties of the anterior cruciate ligament or the patellar tendon of cynomolgus macaques.

CLINICAL RELEVANCE

This study supports the idea that knee ligament injury in female athletes is not a direct result of estrogen's effect on ligament properties.

Influence of gender, estrogen and exercise on anterior knee laxity

BACKGROUND

Researchers have theorized that the disproportionate number of anterior cruciate ligament injuries in females, as compared to males, may be related to knee laxity, which in turn may be influenced by hormones. The purpose of this study was to investigate the collective effects of gender, estrogen and exercise on knee laxity.

METHODS

Subjects consisted of 12 females and 12 males with no history of lower extremity injury. Serum estrogen levels and knee laxity were measured for the female subjects at specific times to represent three menstrual cycle phases while knee laxity of the male subjects was measured on three different days. For each data collection session, knee laxity was measured just prior to and immediately following an exercise protocol. Separate repeated measures ANOVAs were used to compare estrogen levels across the phases and analyze the laxity data.

FINDINGS

Females exhibited greater knee laxity than males both pre- and post-exercise across all phases of the menstrual cycle. Estrogen fluctuations across the menstrual cycle did not modify knee laxity in females. Prior exercise induced equivalent increases in knee laxity in males and females across the data collection periods and irrespective of estrogen concentration.

INTERPRETATION

If the anterior cruciate ligament is more distensible during athletic activities, it may be less capable of providing the necessary stability in order to prevent injury. This decreased stability may be contributing to the female athlete's increased incidence of anterior cruciate ligament injury. Overall, if females experience greater knee laxity during athletic activities, specific training strategies to compensate for these differences are warranted.

Quantitation of estrogen receptors and relaxin binding in human anterior cruciate ligament fibroblasts

The significantly higher incidence of anterior cruciate ligament (ACL) injuries in collegiate women compared with men may result from relative ligament laxity. Differences in estrogen and relaxin activity, similar to that seen in pregnancy, may account for this. We quantified estrogen receptors by flow cytometry and relaxin receptors by radioligand binding assay in human ACL cells and compared the presence of these receptors in males and females. ACL stumps were harvested from seven males and eight females with acute ACL injuries. The tissue was placed in M199 cell culture medium. Outgrowth cultures were obtained, and passage 2 cells were used for all studies. Estrogen receptor determination was performed using flow cytometry. Relaxin binding was performed in ACL cells derived from five female and male patients using I(125)-labeled relaxin. Estrogen receptors were identified by flow cytometry in 4 to 10% of ACL cells. Mean fluorescence of cells expressing estrogen receptors was approximately twice that of controls, with no significant differences between males and females. Relaxin studies showed low-level binding of I(125)-relaxin-labeled ACL cells. Relaxin binding was present in four out of five female ACL cells versus one out of five male ACL cells.

Neuromuscular performance and knee laxity do not change across the menstrual cycle in female athletes

Female athletes incur anterior cruciate ligament ruptures at a rate at least twice that of male athletes. Hypothesized factors for the increased injury risk in females include biomechanical, neuromuscular, and hormonal differences between genders. A wealth of literature exists examining these potential predispositions individually, but the interactions between these factors have not been examined extensively. Our purpose was to investigate changes in neuromuscular control and laxity at the knee across the menstrual cycle of healthy females. Fourteen female collegiate athletes with normal, documented ovulatory menstrual cycles, confirmed ovulation, and no history of serious knee injury participated. The presence and timing of ovulation was determined during a screening cycle with ovulation detection kits and during an experimental cycle with collection of daily urine samples and subsequent analysis of urinary estrone-3-glucuronide (E3G) and pregnanediol-3-glucoronide (PdG), which correlate with circulating estrogen and progesterone. Each subject had measures of knee neuromuscular performance and laxity once during the mid-follicular, ovulatory, and mid-luteal stages of her menstrual cycle. The test battery included assessments of knee flexion and extension peak torque, passive knee joint position sense, and postural control in single leg stance. Knee joint laxity was measured with an arthrometer. Analyses of variance revealed that E3G and PdG levels were significantly different across the three testing sessions, but there were no significant differences in the measures of strength, joint position sense, postural control, or laxity. No significant correlations were found between changes in E3G or PdG levels and changes in the performance and laxity measures between sessions. These results suggest that neuromuscular control and knee joint laxity do not change substantially across the menstrual cycle of females despite varying estrogen and progesterone levels.

Understanding and preventing noncontact anterior cruciate ligament injuries: a review of the Hunt Valley II meeting, January 2005

The incidence of noncontact anterior cruciate ligament injuries in young to middle-aged athletes remains high. Despite early diagnosis and appropriate operative and nonoperative treatments, posttraumatic degenerative arthritis may develop. In a meeting in Atlanta, Georgia (January 2005), sponsored by the American Orthopaedic Society for Sports Medicine, a group of physicians, physical therapists, athletic trainers, biomechanists, epidemiologists, and other scientists interested in this area of research met to review current knowledge on risk factors associated with noncontact anterior cruciate ligament injuries, anterior cruciate ligament injury biomechanics, and existing anterior cruciate ligament prevention programs. This article reports on the presentations, discussions, and recommendations of this group.

The menstrual cycle and sport performance

The female sex steroid hormones estrogen and progesterone have potential effects on exercise capacity and performance through numerous mechanisms, such as substrate metabolism, cardiorespiratory function, thermoregulation, psychologic factors, and injuries. Consequently, hormone level changes may theoretically lead to either improved or decreased performance at various times throughout the menstrual cycle. Numerous methodological issues and a paucity of studies have precluded evidence-based conclusions in almost every area of research in this field. In addition, there appears to be a great degree of inter- and intraindividual variability in these hormonal responses. Using oral contraceptives may be advantageous for female athletes who are negatively affected by their menstrual cycle, as they may provide a stable yet controllable hormonal milieu for training and competition.

Maturation leads to gender differences in landing force and vertical jump performance: a longitudinal study

BACKGROUND

Female athletes have increased risk of anterior cruciate ligament rupture after the onset of puberty.

HYPOTHESES

Male athletes would demonstrate a longitudinal increase in vertical jump height compared with female athletes. There would be longitudinal gender differences in ground-reaction forces and loading rates.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

Sixteen female and 17 male adolescent athletes were evaluated for 2 consecutive years. Subjects were included if they were classified as pubertal during the first year of testing and postpubertal during the second year. As subjects performed a drop vertical jump, ground-reaction force, and vertical jump height were measured. Data analysis consisted of a mixed design analysis of variance with post hoc analysis (paired t tests).

RESULTS

The male athletes demonstrated increased vertical jump height with maturation (P < .001); female athletes did not. Boys significantly reduced their landing ground-reaction force (P = .005), whereas girls did not. Takeoff force decreased in girls (P = .003) but not in boys. Both boys and girls had decreased loading rates with maturation (P < .001); however, girls had higher loading rates than did boys at both stages of maturation (P = .037).

CONCLUSION

Male athletes demonstrated a neuromuscular spurt as evidenced by increased vertical jump height and increased ability to attenuate landing force. The absence of similar adaptations in female athletes may be related to the increased risk of anterior cruciate ligament injury.