Melissa M. Montgomery

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 (ICC2,3 = 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.

Cyclic variations in multiplanar knee laxity influence landing biomechanics.

PURPOSE Females vary substantially in their multiplanar cyclic knee laxity changes across the menstrual cycle. The biomechanical implications of these cyclic changes are relatively unknown. Our purpose was to first cluster females based on their cyclic changes in anterior knee laxity (AKL), genu recurvatum (GR), varus-valgus (VV), and internal-external (IER) rotation knee laxity across the menstrual cycle. We then compared changes in landing biomechanics from days of minimum to maximum laxity between female clusters and a group of males. METHODS A total of 49 males and 71 females were measured for AKL, GR, VV, and IER and underwent biomechanical analysis of a double-leg drop jump (0.45 m) at two time points: day of minimum (T₁) and maximum (T₂) AKL in each female across her menstrual cycle (males matched in time). Cluster analysis identified four distinct patterns of multiplanar cyclic knee laxity changes from T₁ to T₂ (C₁-C₄). Males were classified as a separate group. RESULTS When landing from a jump, female clusters who increased both sagittal and frontal plane laxity from T₁ to T₂ (C₃, C₄) had 3.7° to 5.2° greater net movement toward knee valgus from T₁ to T₂ compared with females who did not increase both sagittal and frontal plane laxity (C₁) (P = 0.041). Females who increased IER without increasing AKL from T₁ to T₂ (C₂) had -3.7° to -8.1° greater net movement toward knee internal rotation when compared with females who increased both AKL and IER (C₃, C₄) or males who maintained similar laxity from T1 to T2. CONCLUSIONS Changes in knee joint kinematics across the menstrual cycle were dependent on both the absolute and the relative magnitude of multiplanar knee laxity changes. The combination of relatively greater knee valgus coupled with relatively greater external rotation in those with large multiplanar knee laxity changes (C₄) suggests an increased susceptibility to high-risk knee joint positions on ground contact and early in the landing phase.

Associations Between Lower Extremity Muscle Mass and Multiplanar Knee Laxity and Stiffness A Potential Explanation for Sex Differences in Frontal and Transverse Plane Knee Laxity

Background: Compared with men, women have disproportionally greater frontal (varus-valgus) and transverse (internal-external) plane laxity and lower stiffness, despite having similar sagittal (anterior-posterior) plane laxity and stiffness. While the underlying cause is unclear, the amount of lower extremity lean mass (LELM) may be a contributing factor. Hypothesis: Lower extremity lean mass would be a stronger predictor of frontal and transverse plane laxity and incremental stiffness than the sagittal plane. Associations between LELM and stiffness would be stronger at lower force increments. Study Design: Descriptive laboratory study. Methods: Sixty-three women and 30 men with no history of ligament injury were measured for knee laxity and incremental stiffness in the sagittal (−90- to 130-N posterior-to-anterior directed loads), frontal (±10-N·m varus-valgus torques), and transverse (±5-N·m internal-external rotation torques) planes and underwent dual-energy X-ray absorptiometry scans to measure LELM. Linear regressions examined the extent to which LELM predicted each laxity and stiffness value, while also accounting for a person’s sex. Results: Females (vs males) had greater laxity and less stiffness in the frontal and transverse planes but not the sagittal plane. Lower extremity lean mass was a poor predictor of sagittal laxity and stiffness (R2 range = .021-.081; P > .06) but was a stronger predictor of frontal (R2 range = .215-.567; P < .01) and transverse (R2 range = .224-.356; P < .01) plane laxity and stiffness. Associations were stronger for low (R2 = .495-.504) versus high (R2 = .215-.435) frontal plane stiffness but were similar for low (R2 = .233-.293) versus high (R2 = .224-.356) transverse plane stiffness. Once we accounted for a person’s LELM, sex had little effect on laxity and stiffness (change in R2 after removal = .01-.08; P = .027-.797). Conclusion: Less LELM was associated with greater laxity and less stiffness in frontal and transverse planes, which may contribute to the disproportionally higher laxities and reduced stiffnesses observed in females in these planes. Clinical Relevance: Frontal and transverse plane laxity and stiffness may be modifiable through strength training interventions that promote changes in muscle characteristics (eg, muscle cross-sectional area, stiffness) that may contribute to static knee joint stability, thus dynamic joint stability during sport activity.

Knee Joint Laxity and Its Cyclic Variation Influence Tibiofemoral Motion during Weight Acceptance

PURPOSE to better understand how sex differences in anterior knee laxity (AKL) affect knee joint biomechanics, we examined the consequence of greater absolute baseline (males and females) and cyclic increases in AKL during the menstrual cycle (females) on anterior tibial translation (ATT) as the knee transitioned from non-weight-bearing to weight-bearing conditions, while also controlling for genu recurvatum (GR). METHODS males and females (71 females and 48 males, aged 18-30 yr) were measured for AKL and GR and underwent measurement of ATT. Women were tested on the days of their cycle when AKL was at its minimum (T1) and maximum (T2); males were matched in time to a female with similar AKL. Linear regressions examined relationships between absolute baseline (AKLT1, GRT1) and cyclic changes (Δ = T2 - T1; AKLΔ, GRΔ) (females only) in knee laxity with ATT as measured at T1 and T2 and Δ (T2 - T1) (females only). RESULTS AKL and GR increased in females, but not in males, from T1 to T2. Greater AKLT1 and GRT1 predicted greater ATTT1 and ATTT2 in males (R = 21.0, P < 0.007). The combination of greater AKLT1, AKLΔ, and less GRΔ predicted greater ATTT1 and ATTT2 in females (R = 12.5-13.1, P < 0.05), with AKLΔ being a stronger predictor (coefficient, P value) of ATTT2 (0.864, P = 0.027) compared with ATTT1 (0.333, P = 0.370). AKLΔ was the sole predictor of ATTΔ (R = 0.104 and 0.740, P = 0.042). CONCLUSIONS greater absolute baseline and cyclic increases in AKL were consistently associated with greater ATT produced by transition of the knee from non-weight-bearing to weight-bearing. Because the anterior cruciate ligament is the primary restraint to ATT, these findings provide insight into the possible mechanisms by which greater AKL may be associated with at-risk knee biomechanics during the weight acceptance phase of dynamic tasks.

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.

Methodological considerations of task and shoe wear on joint energetics during landing

To better understand methodological factors that alter landings strategies, we compared sagittal plane joint energetics during the initial landing phase of drop jumps (DJ) vs. drop landings (DL), and when shod vs. barefoot. Surface electromyography, kinematic and kinetic data were obtained on 10 males and 10 females during five consecutive drop landings and five consecutive drop jumps (0.45m) when shod and when barefoot. Energy absorption was greater in the DJ vs. DL (P=.002), due to increased energy absorption at the hip during the DJ. Joint stiffness/impedance was more affected by shoe condition, where overall stiffness/impedance was greater in shod compared to barefoot conditions (P=.036). Further, hip impedance was greater in shod vs. barefoot for the DL only (via increased peak hip extensor moment in DL), while ankle stiffness was greater in the barefoot vs. shod condition for the DJ only (via decreased joint excursion and increased peak joint moment in DJ vs. DL) (P=.011). DJ and DL place different neuromechanical demands upon the lower extremities, and shoe wear may alter impact forces that modulate stiffness/impedance strategies. The impact of these methodological differences should be considered when comparing landing biomechanics across studies.

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.

Influence of Lean Body Mass and Strength on Landing Energetics

PURPOSE Less lean body mass may limit ones ability to produce adequate muscle forces to safely control landing from a jump, thus increasing the risk for injury. The primary objective of this study was to determine the effect of lower extremity lean mass (LELM) and eccentric muscle strength on lower extremity energy absorption (EA) during a drop jump landing. METHODS Seventy athletic subjects (35 men and 35 women) were measured for LELM with dual-energy x-ray absorptiometry, maximal eccentric strength of the quadriceps (QuadECC) and hamstrings (HamECC), and lower extremity joint energetics during the initial landing of a drop jump. A mediation analysis examined the extent to which LELM predicted EA at each lower extremity joint (EAHIP, EAKNEE, and EAANK) and subsequently whether these relationships were mediated by each subjects maximal eccentric strength capabilities. RESULTS LELM was a significant predictor of EAKNEE (R = 0.22, P < 0.01) in females but not in males (R = 0.03, P = 0.16). In females, QuadECC was a significant mediator of the effect of LELM on EA at the knee (ab = 179.72, 95% confidence interval [CI] = 10.43-423.42) and ankle (ab = 1.71, 95% CI = [0.16, 3.94]), whereas HamECC was a significant mediator of the relationship between LELM and EAHIP (ab = 4.89, 95% CI = 2.05-8.40). No significant relationships were observed in males. CONCLUSIONS LELM was a significant factor in energetic capabilities for females but not males. For females, this relationship was evident secondary to the stronger underlying relationship between maximal strength and EA. Thus, the maximal eccentric strength capabilities may be a more important determinant of energetic behaviors compared with the available quantity of lean mass alone. More work is needed to investigate these relationships and to reveal the underlying sex-specific mechanisms that determine EA capabilities.

Changes in serum collagen markers, IGF‐I, and Knee joint laxity across the menstrual cycle

Variations in serum markers of collagen production (CICP) and degradation (ICTP), insulin‐like growth factor I (IGF‐I) and anterior knee laxity (AKL) were measured in 20 women [10 with spontaneous cycles (eumenorrheic), 10 using oral contraceptives] over 5 consecutive days at menses (M1–M5, 1st pill week), the initial estrogen rise near ovulation (O1–O5, 2nd pill week), the initial progesterone rise of the early luteal phase (EL1–EL5, 3rd pill week) and post‐progesterone peak of the late luteal phase (LL1–LL5, 4th pill week). ICTP was higher in oral contraceptive women (5.3 ± 1.7 vs. 3.7 ± 1.3 µg/L; p = 0.030), primarily during days near ovulation and the early luteal phase when concentrations decreased in eumenorrheic women (p = 0.04). IGF‐I concentrations increased during menses then decreased and remained lower during the early and late luteal phase in oral contraceptive women, resulting in lower concentrations compared to eumenorrheic women at EL2 and LL1 (p = 0.03). CICP decreased in early and late luteal days (p <0.01), and there was a trend toward lower concentrations in eumenorrheic versus oral contraceptive women (85.7 ± 35.7 ng/ml vs. 123.2 ± 49.8 ng/ml; p = 0.07). Lower CICP and greater IGF‐I concentrations predicted greater AKL across the 20 cycle days in both groups (R2 = 0.310 and 0.400). Sex hormone concentration changes across the menstrual cycle are of sufficient magnitude to influence collagen metabolism, and may indirectly influence knee structure and function.

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.