The relationship between menstrual cycle phase and anterior cruciate ligament injury: a case-control study of recreational alpine skiers

Evaluation of an Algorithm to Predict Menstrual-Cycle Phase at the Time of Injury

CONTEXT

Women are 2 to 8 times more likely to sustain an anterior cruciate ligament (ACL) injury than men, and previous studies indicated an increased risk for injury during the preovulatory phase of the menstrual cycle (MC). However, investigations of risk rely on retrospective classification of MC phase, and no tools for this have been validated.

OBJECTIVE

To evaluate the accuracy of an algorithm for retrospectively classifying MC phase at the time of a mock injury based on MC history and salivary progesterone (P4) concentration.

DESIGN

Descriptive laboratory study.

SETTING

Research laboratory.

PARTICIPANTS

Thirty-one healthy female collegiate athletes (age range, 18-24 years) provided serum or saliva (or both) samples at 8 visits over 1 complete MC.

MAIN OUTCOME MEASURE(S)

Self-reported MC information was obtained on a randomized date (1-45 days) after mock injury, which is the typical timeframe in which researchers have access to ACL-injured study participants. The MC phase was classified using the algorithm as applied in a stand-alone computational fashion and also by 4 clinical experts using the algorithm and additional subjective hormonal history information to help inform their decision. To assess algorithm accuracy, phase classifications were compared with the actual MC phase at the time of mock injury (ascertained using urinary luteinizing hormone tests and serial serum P4 samples). Clinical expert and computed classifications were compared using κ statistics.

RESULTS

Fourteen participants (45%) experienced anovulatory cycles. The algorithm correctly classified MC phase for 23 participants (74%): 22 (76%) of 29 who were preovulatory/anovulatory and 1 (50%) of 2 who were postovulatory. Agreement between expert and algorithm classifications ranged from 80.6% (κ = 0.50) to 93% (κ = 0.83). Classifications based on same-day saliva sample and optimal P4 threshold were the same as those based on MC history alone (87.1% correct). Algorithm accuracy varied during the MC but at no time were both sensitivity and specificity levels acceptable.

CONCLUSIONS

These findings raise concerns about the accuracy of previous retrospective MC-phase classification systems, particularly in a population with a high occurrence of anovulatory cycles.

The influence of sex hormones on anterior cruciate ligament rupture: female study

PURPOSE

The purpose of this study was to determine the difference in the concentrations of testosterone, 17-β estradiol and progesterone between female patients with and without ACL rupture and the possible effect of these hormones on generalised joint laxity.

METHODS

Female subjects with non-contact knee joint injury were included in this study. They were divided into two groups: the examined group, consisting of female subjects with ACL rupture, and the control group, consisting of female patients without ACL rupture. In the next step, the patients from these two groups were paired off on the basis of three factors: the level of professional sports involvement (including the type of sports activity), the side of the body where the injury had occurred (left or right) and the age of the subjects. In the end, there were 12 pairs (24 subjects). The concentrations of sex hormones were established from saliva specimens with the aid of the Salimetrics enzyme immunoassay. Generalised joint laxity was tested with the aid of the "laxity score" according to Beighton, Solomon and Soskolne.

RESULTS

Female subjects with ACL rupture had significantly lower concentrations of testosterone (p < 0.01), significantly lower concentrations of 17-β estradiol (p < 0.05) and significantly lower concentrations of progesterone (p < 0.01) than female subjects with intact ACL.

CONCLUSIONS

Decreased concentrations of testosterone, 17-β estradiol or progesterone may be a risk factor leading to ACL rupture. The concentrations of these hormones do not affect generalised joint laxity. Additional research on a larger group of patients is necessary to further determine the effects of these hormones on generalised joint laxity and ACL ruptures. Young female athletes with lower concentrations of sex hormones are more prone to anterior cruciate ligament rupture which is why they need to reduce their sports activities during the pre-ovulatory phase of the menstrual cycle, when these concentrations are additionally reduced.

High knee abduction moments are common risk factors for patellofemoral pain (PFP) and anterior cruciate ligament (ACL) injury in girls: is PFP itself a predictor for subsequent ACL injury?

BACKGROUND

Identifying risk factors for knee pain and anterior cruciate ligament (ACL) injury can be an important step in the injury prevention cycle.

OBJECTIVE

We evaluated two unique prospective cohorts with similar populations and methodologies to compare the incidence rates and risk factors associated with patellofemoral pain (PFP) and ACL injury.

METHODS

The 'PFP cohort' consisted of 240 middle and high school female athletes. They were evaluated by a physician and underwent anthropometric assessment, strength testing and three-dimensional landing biomechanical analyses prior to their basketball season. 145 of these athletes met inclusion for surveillance of incident (new) PFP by certified athletic trainers during their competitive season. The 'ACL cohort' included 205 high school female volleyball, soccer and basketball athletes who underwent the same anthropometric, strength and biomechanical assessment prior to their competitive season and were subsequently followed up for incidence of ACL injury. A one-way analysis of variance was used to evaluate potential group (incident PFP vs ACL injured) differences in anthropometrics, strength and landing biomechanics. Knee abduction moment (KAM) cut-scores that provided the maximal sensitivity and specificity for prediction of PFP or ACL injury risk were also compared between the cohorts.

RESULTS

KAM during landing above 15.4 Nm was associated with a 6.8% risk to develop PFP compared to a 2.9% risk if below the PFP risk threshold in our sample. Likewise, a KAM above 25.3 Nm was associated with a 6.8% risk for subsequent ACL injury compared to a 0.4% risk if below the established ACL risk threshold. The ACL-injured athletes initiated landing with a greater knee abduction angle and a reduced hamstrings-to-quadriceps strength ratio relative to the incident PFP group. Also, when comparing across cohorts, the athletes who suffered ACL injury also had lower hamstring/quadriceps ratio than the players in the PFP sample (p<0.05).

CONCLUSIONS

In adolescent girls aged 13.3 years, >15 Nm of knee abduction load during landing is associated with greater likelihood of developing PFP. Also, in girls aged 16.1 years who land with >25 Nm of knee abduction load during landing are at increased risk for both PFP and ACL injury.

Is the use of oral contraceptives associated with operatively treated anterior cruciate ligament injury? A case-control study from the Danish Knee Ligament Reconstruction Registry

BACKGROUND

The incidence of anterior cruciate ligament (ACL) injuries is 2 to 9 times higher in women than in men. In addition, in vitro studies have demonstrated that ACL is an estrogen target tissue, and some studies have therefore suggested a protective association between oral contraceptives (OC) and the likelihood of sustaining ACL injury.

HYPOTHESIS

There is a protective association between OC use and the likelihood of operatively treated ACL injury.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

The study population included 4497 women with an operatively treated ACL injury registered in the Danish Knee Ligament Reconstruction Registry for the 2005 to 2011 period and 8858 age-matched controls with no ACL injury. The study evaluated exposure to OC use at the time of ACL injury (index date) and in the 5 previous years ("ever user") or no OC use ("never user"). Ever users were further classified as either new users (patients who redeemed their first prescription within the first year before the index date), long-term users (redeemed additional prescriptions 1 to 5 years before the index date), or recent users (redeemed their most recent prescription >1 year before the index date). Finally, a dose-response analysis of OC use was performed. Conditional logistic regression was used to calculate the relative risk (RR) with a 95% CI of sustaining an operatively treated ACL injury according to OC use.

RESULTS

The adjusted RR associating OC with ACL injury was 0.82 (95% CI, 0.75-0.90) between ever users and never users. Furthermore, there was a decreased RR of sustaining ACL injury of 0.80 (95% CI, 0.74-0.91) in long-term users and 0.81 (95% CI, 0.72-0.89) in recent users. Using OC for more than 4 years did not seem to alter the likelihood of sustaining an operatively treated ACL injury.

CONCLUSION

This population-based pharmacoepidemiological study including 13,355 women indicates that a protective association exists between OC use and the likelihood of sustaining an operatively treated ACL injury. Although this study does indicate a protective association of OC use, OC should not be used as a prophylactic measure before additional clinical studies have further clarified the biological and causal association between OC use and the likelihood of sustaining operatively treated ACL injury.

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.

The effect of relaxin on the musculoskeletal system

Relaxin is a hormone structurally related to insulin and insulin-like growth factor, which exerts its regulatory effect on the musculoskeletal and other systems through binding to its receptor in various tissues, mediated by different signaling pathways. Relaxin alters the properties of cartilage and tendon by activating collagenase. This hormone is also involved in bone remodeling and healing of injured ligaments and skeletal muscle. In this review, we have summarized the literature on the effect of relaxin in musculoskeletal system to provide a broad perspective for future studies in this field.

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.

Sex differences, hormone fluctuations, ankle stability, and dynamic postural control

CONTEXT

Hormonal fluctuation as a risk factor in anterior cruciate ligament injury has been investigated with conflicting results. However, the influence of hormone fluctuations on ankle laxity and function has not been thoroughly examined.

OBJECTIVE

To examine the potential hormone contributions to ankle laxity and dynamic postural control during the preovulatory and postovulatory phases of the menstrual cycle using an ankle arthrometer and the Star Excursion Balance Test in healthy women. The cohort group consisted of male control participants.

DESIGN

Cohort study.

SETTING

Research laboratory.

PATIENTS OR OTHER PARTICIPANTS

Twenty healthy women (age = 23.8 ± 6.50 years, height = 163.88 ± 8.28 cm, mass = 63.08 ± 12.38 kg) and 20 healthy men (age = 23.90 ± 4.15 years, height = 177.07 ± 7.60 cm, mass = 80.57 ± 12.20 kg).

INTERVENTION(S)

Ankle stability was assessed with anterior-posterior and inversion-eversion loading. Dynamic postural control was assessed with the posteromedial reaching distance of the Star Excursion Balance Test.

MAIN OUTCOME MEASURE(S)

Female participants used ovulation kits for 3 months to determine the time of ovulation; during their preovulatory and postovulatory phases, they were tested in the laboratory with an ankle arthrometer and the Star Excursion Balance Test. Male participants were tested on similar dates as controls. For each dependent variable, a time by side by sex repeated-measures analysis of variance was performed. Statistical significance was set a priori at P < .05.

RESULTS

For anterior-posterior laxity, a side main effect was noted (F₁,₃₈ = 10.93, P = .002). For inversion-eversion laxity, a sex main effect was seen (F₁,₃₈ = 10.75, P = .002). For the posteromedial reaching task, a sex main effect was demonstrated (F₁,₃₈ = 8.72, P = .005). No influences of time on the dependent variables were evident.

CONCLUSIONS

Although women presented with more ankle inversion-eversion laxity and less dynamic postural control, hormonal fluctuations during the menstrual cycle (preovulatory compared with postovulatory) did not affect ankle laxity or dynamic postural control, 2 factors that are associated with ankle instability.

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.

Risk factors for anterior cruciate ligament injury: a review of the literature-part 2: hormonal, genetic, cognitive function, previous injury, and extrinsic risk factors

CONTEXT

Injuries to the anterior cruciate ligament (ACL) are immediately disabling and are associated with long-term consequences, such as posttraumatic osteoarthritis. It is important to have a comprehensive understanding of all possible risk factors for ACL injury to identify individuals who are at risk for future injuries and to provide an appropriate level of counseling and programs for prevention.

OBJECTIVE

This review, part 2 of a 2-part series, highlights what is known and still unknown regarding hormonal, genetic, cognitive function, previous injury, and extrinsic risk factors for ACL injury.

DATA SOURCES

Studies were identified from MEDLINE (1951-March 2011) using the MeSH terms anterior cruciate ligament, knee injury, and risk factors. The bibliographies of relevant articles and reviews were cross-referenced to complete the search.

STUDY SELECTION

Prognostic case-control and prospective cohort study designs to evaluate risk factors for ACL injury were included in this review.

RESULTS

A total of 50 case-control and prospective cohort articles were included in parts 1 and 2. Twenty-one focused on hormonal, genetic, cognitive function, previous injury, and extrinsic risk factors.

CONCLUSIONS

Several risk factors are associated with increased risk of suffering ACL injury-such as female sex, prior reconstruction of the ACL, and familial predisposition. These risk factors most likely act in combination with the anatomic factors reviewed in part 1 of this series to influence the risk of suffering ACL injury.

Effect of pregnancy and obesity on arch of foot

OBJECTIVE

Endocrine changes occurring during pregnancy result in increased laxity of the ligaments of the foot. This may lead to gradual collapse of the foot arches. The aim of the study was to determine whether pregnancy and body mass index (BMI) had a role in affecting the foot arches at long term.

METHODS

A collapsed arch results in widening of the feet, thus altering the foot size. The control group included nulliparous women, while the study group included women who had been pregnant at least once. The groups were stratified secondarily by obesity according to BMI. We reviewed over 1000 charts at the outpatient offices in a large Mid-Western city. The age, BMI, and shoe size in an athletic shoe were recorded.

RESULTS

There were 40 subjects in the control group and 70 in the study group. 19/40 women in control and 46/70 in study group experienced a change in shoe size (P = 0.06). Of those affected, the non-obese control group experienced a 9.7% change in shoe size while the obese study group experienced a 15.5% change (P < 0.05).

CONCLUSION

There was neither a change in size between women who had been pregnant and the nulliparous, nor was there a difference between the obese and non-obese. However, there was a statically significant difference between those affected who were both non-obese and nulliparous and those who had been pregnant and who are obese. Individually, the effect of pregnancy and BMI are highly suggestive and clinically relevant.

Leg dominance is a risk factor for noncontact anterior cruciate ligament injuries in female recreational skiers

BACKGROUND

In recreational alpine skiing, the knee joint accounts for about one third of all injuries in male and female skiers. However, female recreational skiers have twice the knee injury incidence of male skiers, and the anterior cruciate ligament (ACL) injury risk is 3 times greater in female skiers.

PURPOSE

To evaluate whether leg dominance is a risk factor for noncontact ACL injuries in female recreational skiers.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

The relationships between leg dominance, side of knee injury, and gender were analyzed in 65 male and 128 female skiers suffering from a noncontact ACL rupture.

RESULTS

Anterior cruciate ligament ruptures of the left knee occurred more frequently in female than in male recreational skiers (68% vs 48%, P = .006). For both genders, in 90%, the right leg was the preferred kicking leg. With regard to leg dominance, female skiers suffered more often from ACL ruptures of their nondominant leg than male skiers (63% vs 45%, P = .020). An adjusted odds ratio of 2.0 (95% confidence interval, 1.0-3.8) was calculated.

CONCLUSION

Female skiers showed a 2-fold higher risk of suffering from an ACL rupture on their nondominant leg. Therefore, leg dominance seems to be a risk factor for noncontact ACL injuries in female recreational skiers.

Estrogen and muscle stiffness have a negative relationship in females

PURPOSE

Hormonal fluctuations are one potential reason why females might have a greater rate of noncontact ACL injury. The hamstrings are capable of limiting anterior cruciate ligament (ACL) loading. This study examined whether relationships existed between reproductive hormones (estradiol-β-17, free testosterone, and progesterone) and hamstring neuromechanical variables (hamstring musculotendinous stiffness (MTS), rate of force production (RFP), time to 50% peak torque (T50%), and electromechanical delay (EMD)) in genders combined and independently.

METHODS

Muscle properties of the hamstrings and reproductive hormones were evaluated in 30 subjects (15 males and 15 females) that were free from lower extremity injury and had no history of ACL injury. Females were tested 3-5 days after the onset of menses and were not using oral contraceptive. Pearson correlation coefficients were calculated for each hormone and muscle property.

RESULTS

For genders combined, estrogen (mean = 46.0 ± 28.2 pg/mL) was negatively correlated with RFP (mean = 758.8 ± 507.6 N/kg s(-1), r = -0.43, P = 0.02) and MTS (mean = 12.8 ± 2.6 N/cm, r = -0.43, P = 0.02). Free testosterone (mean = 13.2 ± 13.0 pg/mL) was positively correlated with RFP (r = 0.56, P < 0.01) and MTS (r = 0.46, P = 0.01) but negatively correlated with T50% (mean = 114.7 ± 38.9 ms, r = -0.43, P = 0.02). When gender was considered separately, females demonstrated negative correlation between estrogen (mean = 68.0 ± 23.2 pg/mL) and MTS (mean = 11.7 ± 1.5 N/cm, r = -0.53, P = 0.05) and free testosterone (mean = 1.5 ± 0.6 pg/mL) and MTS (r = -0.52, P = 0.05). Males alone displayed no significant correlations between the selected hormones and muscle properties.

CONCLUSIONS

Correlations exist between muscle properties and reproductive hormones. Females, however, may be more sensitive to reproductive hormones and their fluctuations.

Variations in dynamic knee valgus and gluteus medius onset timing in non-athletic females related to hormonal changes during the 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<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.

Isometric knee-extension and knee-flexion torque production during early follicular and postovulatory phases in recreationally active women

CONTEXT

Acute decreases in strength have been associated with risky biomechanical strategies that might predispose one to injury. Whether acute changes in thigh muscle torque occur across the menstrual cycle remains equivocal.

OBJECTIVE

We compared maximal voluntary isometric contraction (MVIC) torque of the knee flexors and extensors between the early follicular (EF) and either the early luteal (EL) or midluteal (ML) phases, which were confirmed by serum hormone concentrations. We expected that MVIC torques would increase from the EF to the EL phase after estradiol peaked and before increased exposure to progesterone.

DESIGN

Cohort study.

SETTING

Applied Neuromechanics Research Laboratory.

PATIENTS OR OTHER PARTICIPANTS

Seventy-one recreationally active women (age range, 18-30 years).

INTERVENTION(S)

The MVICs were measured 1 day during menses and 1 day during the 8 days after ovulation. Participants were grouped by the hormone profile of their luteal test days as EL phase, ML phase, or anovulatory cycle.

MAIN OUTCOME MEASURE(S)

The MVIC torque of knee flexors and extensors (Nm/kg), estradiol (pg/mL), progesterone (ng/mL), and testosterone (ng/dL).

RESULTS

We tested 29 women during their EL phases, 32 during their ML phases, and 10 during anovulatory cycles. Although we observed relatively large individual changes in sex hormone concentrations and MVIC torques across the 2 test sessions, we observed no difference in MVIC torque between test phases (F(1,68)  =  1.17, P  =  .28) or among groups by test phase (F(2,68)  =  0.31, P  =  .74).

CONCLUSIONS

Thigh MVIC torque did not change from time of menses (when estradiol and progesterone were lowest) to time in the luteal phase after an unopposed estradiol rise or combined estradiol and progesterone rise. However, these findings were limited to MVIC torque production measured at 2 different times, and further research examining these relationships at multiple times and using other measures of neuromuscular function is needed.

The intrinsic risk factors for ACL ruptures: an evidence-based review

This article aims to assess the evidence related to the intrinsic risk factors for anterior cruciate ligament (ACL) ruptures. The level of evidence (according to evidence-based guidelines) for each study and the level of certainty for each risk factor were determined. After a review of the evidence, femoral notch geometry was the only risk factor that was found to be associated with risk of ACL rupture with high certainty. This review concludes that more research, particularly high-quality, prospective studies, are required to provide accurate measures of risk. These data should be used to establish multifactorial risk factor models designed to identify individuals at high risk of sustaining an ACL injury.

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.

Some sex hormone profiles are consistent over time in normal menstruating women: implications for sports injury epidemiology

PURPOSE

It is unclear whether sex hormone profiles obtained in two consecutive months are consistent within women. Month-to-month consistency in daily, nadir, peak and mean hormone concentrations during the early follicular and luteal phases in recreationally active, young eumenorrheic women was prospectively examined.

METHODS

60 healthy, non-smoking women who reported normal and consistent menstrual cycles lasting 26-32 days for the past 6 months were followed prospectively to obtain serum samples for the first 6 days of menses and for 8 days after a positive ovulation test over two consecutive months. Month-to-month consistency of daily concentrations of oestradiol (pg/ml), progesterone (ng/ml), testosterone (ng/dl), sex hormone-binding globulin (nmol/l) and free androgen index were determined using linear mixed models. Month-to-month consistency in nadir, peak and mean concentrations were then assessed using intraclass correlation coefficients and SEM to more precisely examine intraindividual consistency.

RESULTS

Linear mixed models revealed stable hormone concentrations across cycles and cycles by day. Reliability estimates for nadir, peak, mean menses and mean postovulatory concentrations range from 0.56 to 0.86 for oestradiol, 0.44 to 0.91 for progesterone, 0.60 to 0.86 for testosterone, 0.88 to 0.97 for sex hormone-binding globulin and 0.78 to 0.91 for free androgen index.

CONCLUSIONS

Hormone profiles were reproducible over two consecutive months. To reduce month-to-month intraindividual variations and improve measurement consistency, it is recommended that multiple samples be taken over consecutive days as opposed to a single sample.

Reducing the risk of noncontact anterior cruciate ligament injuries in the female athlete

High school and collegiate female athletes have a significantly increased risk of sustaining a noncontact anterior cruciate ligament injury compared with male athletes participating in the same sport. This review summarizes the current knowledge of the risk factors hypothesized to influence this problem, and the neuromuscular training programs designed to correct certain biomechanical problems noted in female athletes. The risk factors include a genetic predisposition for sustaining a knee ligament injury, environmental factors, anatomical indices, hormonal influences, and neuromuscular factors. The greatest amount of research in this area has studied differences between female and male athletes in movement patterns during athletic tasks; muscle strength, activation, and recruitment patterns; and knee joint stiffness under controlled, preplanned, and reactive conditions in the laboratory. Neuromuscular retraining programs have been developed in an attempt to reduce these differences. The successful programs teach athletes to control the upper body, trunk, and lower body position; lower the center of gravity by increasing hip and knee flexion during activities; and develop muscular strength and techniques to land with decreased ground reaction forces. In addition, athletes are taught to preposition the body and lower extremity prior to initial ground contact to obtain the position of greatest knee joint stability and stiffness. Two published programs have significantly reduced the incidence of noncontact anterior cruciate ligament injuries in female athletes participating in basketball, soccer, and volleyball. Other programs were ineffective, had a poor study design, or had an insufficient number of participants, which precluded a true reduction in the risk of this injury. In order to determine which risk factors for noncontact anterior cruciate ligament ruptures are significant, future investigations should include larger cohorts of athletes in multiple sports, analyze factors from all of the major risk categories, and follow athletes for at least one full athletic season. Future risk assessment studies should incorporate reactive tasks under more realistic sports conditions.

Are oral contraceptive use and menstrual cycle phase related to anterior cruciate ligament injury risk in female recreational skiers?

Oral contraceptive use and menstrual cycle phase are suggested to influence the risk of anterior cruciate ligament (ACL) injuries in female athletes. However, only few data are available for recreational sports. Therefore, female recreational skiers with a non-contact ACL injury and age-matched controls completed a self-reported questionnaire relating to menstrual history, oral contraceptive use and previous knee injuries. Menstrual history data were used to group subjects into either preovulatory or postovulatory phases of menstrual cycle. Our findings suggest that oral contraceptive use did not show any protective effect against ACL injuries nor did self-reported previous knee injuries show any association with ACL injury rate in recreational alpine skiing. Analysis of menstrual history data revealed that recreational skiers in the preovulatory phase were significantly more likely to sustain an ACL injury than were skiers in the postovulatory phase.

Prevention of non-contact anterior cruciate ligament injuries in soccer players. Part 1: Mechanisms of injury and underlying risk factors

Soccer is the most commonly played sport in the world, with an estimated 265 million active soccer players by 2006. Inherent to this sport is the higher risk of injury to the anterior cruciate ligament (ACL) relative to other sports. ACL injury causes the most time lost from competition in soccer which has influenced a strong research focus to determine the risk factors for injury. This research emphasis has afforded a rapid influx of literature defining potential modifiable and non-modifiable risk factors that increase the risk of injury. The purpose of the current review is to sequence the most recent literature that reports potential mechanisms and risk factors for non-contact ACL injury in soccer players. Most ACL tears in soccer players are non-contact in nature. Common playing situations precluding a non-contact ACL injury include: change of direction or cutting maneuvers combined with deceleration, landing from a jump in or near full extension, and pivoting with knee near full extension and a planted foot. The most common non-contact ACL injury mechanism include a deceleration task with high knee internal extension torque (with or without perturbation) combined with dynamic valgus rotation with the body weight shifted over the injured leg and the plantar surface of the foot fixed flat on the playing surface. Potential extrinsic non-contact ACL injury risk factors include: dry weather and surface, and artificial surface instead of natural grass. Commonly purported intrinsic risk factors include: generalized and specific knee joint laxity, small and narrow intercondylar notch width (ratio of notch width to the diameter and cross sectional area of the ACL), pre-ovulatory phase of menstrual cycle in females not using oral contraceptives, decreased relative (to quadriceps) hamstring strength and recruitment, muscular fatigue by altering neuromuscular control, decreased "core" strength and proprioception, low trunk, hip, and knee flexion angles, and high dorsiflexion of the ankle when performing sport tasks, lateral trunk displacement and hip adduction combined with increased knee abduction moments (dynamic knee valgus), and increased hip internal rotation and tibial external rotation with or without foot pronation. The identified mechanisms and risk factors for non-contact ACL injuries have been mainly studied in female soccer players; thus, further research in male players is warranted. Non-contact ACL injuries in soccer players likely has a multi-factorial etiology. The identification of those athletes at increased risk may be a salient first step before designing and implementing specific pre-season and in-season training programs aimed to modify the identified risk factors and to decrease ACL injury rates. Current evidence indicates that this crucial step to prevent ACL injury is the only option to effectively prevent the sequelae of osteoarthritis associated with this traumatic injury.

Alterations in knee joint laxity during the menstrual cycle in healthy women leads to increases in joint loads during selected athletic movements

BACKGROUND

It has been speculated that the hormonal cycle may be correlated with higher incidence of ACL injury in female athletes, but results have been very contradictory.

HYPOTHESIS

Knee joint loads are influenced by knee joint laxity (KJL) during the menstrual cycle.

STUDY DESIGN

Controlled laboratory study.

METHODS

Serum samples and KJL were assessed at the follicular, ovulation, and luteal phases in 26 women. Knee joint mechanics (angle, moment, and impulse) were measured and compared at the same intervals. Each of the 26 subjects had a value for knee laxity at each of the 3 phases of their cycle, and these were ordered and designated low, medium, and high for that subject. Knee joint mechanics were then compared between low, medium, and high laxity.

RESULTS

No significant differences in knee joint mechanics were found across the menstrual cycle (no phase effect). However, an increase in KJL was associated with higher knee joint loads during movement (laxity effect). A 1.3-mm increase in KJL resulted in an increase of approximately 30% in adduction impulse in a cutting maneuver, an increase of approximately 20% in knee adduction moment, and a 20% to 45% increase in external rotation loads during a jumping and stopping task (P < .05).

CONCLUSION

Changes in KJL during the menstrual cycle do change knee joint loading during movements. Clinical Relevance Our findings will be beneficial for researchers in the development of more effective ACL injury prevention programs.

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.

Knee anterior laxity: a risk factor for traumatic knee injury among sportswomen?

The purpose of this study was to investigate if knee anterior laxity, measured with an arthrometer, is a risk factor for traumatic knee injury in sportswomen. To allow a more complete analysis, other, easily measured variables such as anthropometry, lower leg characteristics, sport exposure and menstrual cycle characteristics were also evaluated as possible risk factors. Subjects were Slovenian sportswomen aged between 11 and 41 years participating in basketball, team handball and volleyball (N = 540). Sportswomen were tested in the pre-season and followed for one season. The data collection included: written informed consent, background questionnaire, anthropometric tests, leg dominance assessment, navicular drop test (measurement of foot pronation), passive knee extension assessment and measurement of knee anterior laxity with a KT arthrometer. Several sets of data analysis were performed including logistic regression analysis in order to build a model for predicting traumatic knee injury among sportswomen. Height and average hours of training per week were found to differ significantly (P < 0.05) between injured and uninjured sportswomen. More sportswomen injured their non-dominant leg. Traumatic knee injuries among Slovenian sportswomen participating in basketball, team handball and volleyball are associated with higher amounts of training, greater body height and greater knee anterior laxity. Only 1% of the variability in traumatic knee injuries among sportswomen were explained with those variables suggesting that there are many other variables associated with traumatic knee injuries among sportswomen than were tested in this study.

Non-contact ACL injuries in female athletes: an International Olympic Committee current concepts statement

The incidence of anterior cruciate ligament (ACL) injury remains high in young athletes. Because female athletes have a much higher incidence of ACL injuries in sports such as basketball and team handball than male athletes, the IOC Medical Commission invited a multidisciplinary group of ACL expert clinicians and scientists to (1) review current evidence including data from the new Scandinavian ACL registries; (2) critically evaluate high-quality studies of injury mechanics; (3) consider the key elements of successful prevention programmes; (4) summarise clinical management including surgery and conservative management; and (5) identify areas for further research. Risk factors for female athletes suffering ACL injury include: (1) being in the preovulatory phase of the menstrual cycle compared with the postovulatory phase; (2) having decreased intercondylar notch width on plain radiography; and (3) developing increased knee abduction moment (a valgus intersegmental torque) during impact on landing. Well-designed injury prevention programmes reduce the risk of ACL for athletes, particularly women. These programmes attempt to alter dynamic loading of the tibiofemoral joint through neuromuscular and proprioceptive training. They emphasise proper landing and cutting techniques. This includes landing softly on the forefoot and rolling back to the rearfoot, engaging knee and hip flexion and, where possible, landing on two feet. Players are trained to avoid excessive dynamic valgus of the knee and to focus on the "knee over toe position" when cutting.

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.

Anterior cruciate ligament biology and its relationship to injury forces

Anterior cruciate ligament injury is determined by two variables: the ultimate failure load of the ligament and the mechanical load applied to the ligament. All factors that contribute to anterior cruciate ligament injury must do so by affecting one or both of these two basic variables. Some factors, such as sex hormones and tissue remodeling, have a multifaceted effect on the failure load of the anterior cruciate ligament and the magnitude of the load applied to it. The model also illustrates the potentially profound effects that sex hormones and tissue remodeling likely have on female susceptibility to anterior cruciate ligament injuries.

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.