The relationship between serum relaxin and knee joint laxity in female athletes

The role of relaxin in anterior cruciate ligament injuries: a systematic review

OBJECTIVE

Anterior cruciate ligament (ACL) tears are exceedingly common among the athletic population and are seen with higher incidence in females. Observational studies have noted peak ACL tear rates in the luteal phase of the menstrual cycle, a time in which the hormone relaxin peaks in serum concentration.

METHODS

A systematic review of the literature was performed. Inclusion criteria specified all prospective and retrospective studies which included the role of relaxin in the pathogenesis of ACL tears.

RESULTS

Six studies met inclusion criteria yielding 189 subjects from clinical studies and 51 in vitro samples. Included studies found that ACL samples exhibit selective relaxin binding. When pre-treated with estrogen prior to relaxin exposure, female ACL tissue samples exhibit increased expression of collagen degrading receptors.

CONCLUSION

Relaxin displays binding specificity to the female ACL and increased serum concentrations are correlated with increased ACL tear rates in female athletes. Further research is needed in this area.

LEVEL OF EVIDENCE

V.

Etiopathogenesis of Canine Cruciate Ligament Disease: A Scoping Review

The spontaneous rupture of the cranial cruciate ligament in dogs remains a pathoetiologic puzzle. Despite much progress in research over the past years, the systemic and local mechanisms leading to ligament degeneration and structural failure remain largely obscure. This scoping review focuses on pathogenesis and aims at summarizing and interpreting today's knowledge on causes of canine cruciate ligament rupture, i.e., the multifactorial mechanisms leading to degenerative stifle joint disease with collagen matrix degeneration and structural failures. Thus, the initial view of traumatic ligament rupture, fostered by "wear and tear", has clearly been replaced by a new concept of systemic processes linked to progressive degenerative joint disease and ligament failure; thus, the term "cranial cruciate ligament disease" has been coined and is generally accepted. In addition, cruciate ligament rupture in people shares some similarities with the lesion in dogs; therefore, the review also includes comparative studies. The methods used were based on the PRISMA-ScR model (Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extension for Scoping Reviews).

Menstrual hormone-induced cyclic thumb CMC instability and degeneration in women: a systematic review

Background

Relaxin is a hormone which peaks during the luteal phase of the menstrual cycle, and a known collagenolytic promoter that has been shown to avidly bind tissues supporting the trapeziometacarpal (TMC) joint in women. We hypothesize a causal linkage between cyclic binding of relaxin to the supporting tissues of the female TMC joint; and to the earlier onset of more severe TMC osteoarthritis (OA) commonly seen in women.

Methods

A systematic literature review was performed per PRISMA guidelines, qualitatively and quantitatively assessing papers regarding relaxin–TMC joint stability interactions. The primary outcome variable was TMC joint degeneration/loss of function; the “late stage” consequences of relaxin-induced instability. The secondary outcome variable was presence of early signs of relaxin-induced instability; specifically asymptomatic TMC joint laxity in young women.

Results

In healthy young women, menstrual cycle relaxin peaks corresponded with asymptomatic TMC joint instability. Immunohistochemical studies of TMC arthroplasty patients showed avidly increased relaxin binding to supporting tissues around the TMC joint in women but not men. Demographic analysis of patients from the TMC arthroplasty studies show a predominantly female cohort, who were on average significantly younger than the male surgical patients.

Conclusions

Each relaxin peak during the menstrual cycle can target receptors on the soft tissues supporting the TMC joint, including—critically—the main stabilizing ligament: the anterior oblique. The cyclic instability is typically asymptomatic for years after menarche, but causes cumulative chondral microtrauma. This likely causes the early-onset, high severity TMC joint OA clinically pervasive among female patients at orthopedic hand clinics. Further research is indicated to develop risk assessment strategies and potential interventional options before and after the onset of hormonal laxity-induced OA.

It is widely recognized among hand surgeons that female patients present at a younger age for basal thumb osteoarthritis, with more severe degeneration.

The little-known menstrual hormone relaxin, which peaks every ovulatory cycle, may be responsible for the female predominance of this pathology.

The soft tissue support structures for the thumb are known to express relaxin receptors which, when activated, trigger lysis of collagen and other extracellular matrix components.

Laxity in soft tissues supporting the thumb, such as the deep anterior oblique ligament, would result in joint instability and microtrauma.

If women cyclically experience thumb instability and cumulative cartilage microtrauma from menarche through menopause, the female propensity to develop TMC arthritis is aptly justified.

Immunoexpression of Relaxin and Its Receptors in Stifle Joints of Dogs with Cranial Cruciate Ligament Disease

Simple Summary

Spontaneous cranial cruciate ligament rupture is one of the most frequently encountered joint diseases in dogs, often leading to disabling chronic progressive osteoarthritis. The cause of the progressive intra-articular collagen matrix degradation, leading to tear and mechanical failure, is unknown. A variety of contributing factors has been found, however, an initiating mediator triggering the collagen degrading cascade remains to be identified. Our finding of strong relaxin- and relaxin receptor expression on intra-articular target tissues, such as on ligament fibrocytes and synovial membranes, renders relaxin a candidate for pathogenetic involvement, for collagen lysis, and progressive ligament fiber disruption. If confirmed, this opens the way for medical treatment of the disease in its early stages. In addition, further proof of relaxin involvement in canine osteoarthritis and ligament rupture would constitute a useful spontaneous animal model for human disease.

Abstract

The etiology of spontaneous cranial cruciate ligament rupture in dogs is unknown despite being one of the most impacting orthopedic diseases in dogs. Numerous studies have contributed to the understanding of a multifactorial pathogenesis, this, however, without identifying a pivotal link to explain progressive collagen degeneration and osteoarthritic changes. In human medicine, recent reports have identified relaxin as a triggering factor in ligament ruptures in knee and metacarpal joints. We thus hypothesized that relaxin might also play a role in canine cruciate ligament rupture. Relaxin’s primarily known property is connective tissue remodeling through collagenolysis. We therefore investigated relaxin and its cognate receptors LGR7/LGR8 in 18 dogs with cranial cruciate ligament disease (CCLD) and compared them to a group of dogs with normal stifle joints. Applying immunohistochemistry (IHC), double immunofluorescence (dIF), and western blot analysis (WB), we found strong and significantly increased expression of both relaxin and its receptors in ruptured cruciate ligaments, and in synovial membranes. Pattern of immuno-staining on dIF strongly suggests relaxin binding to primed receptors and activation of signaling properties, which in turn may have affected collagen matrix metabolism. Thus, in canine cranial cruciate ligament disease, relaxin/receptor signaling may be a primary trigger for collagen fiber degradation and collagen lysis, eventually followed by ligament rupture.

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.

Do Relaxin Levels Impact Hip Injury Incidence in Women? A Scoping Review

PURPOSE

The aim of this review is to assess the current evidence regarding the impact of relaxin on incidence of soft tissue hip injuries in women.

METHODS

A trained research librarian assisted with searches of PubMed, Embase, CINAHL, and SPORTDiscus, with a preset English language filter. The review was completed per the Joanna Briggs Institute (JBI) Manual for Evidence Synthesis methodology. Included studies required assessment of relaxin effects on musculoskeletal health, pelvic girdle stability, or hip joint structures in human subjects. Letters, texts, and opinion papers were excluded.

RESULTS

Our screen yielded 82 studies. Molecularly, relaxin activates matrix metalloproteinases (MMPs) including collagenases MMP-1/-13 and gelatinases MMP-2/-9 to loosen pelvic ligaments for parturition. However, relaxin receptors have also been detected in female periarticular tissues, such as the anterior cruciate ligament, which tears significantly more often during the menstrual cycle peak of relaxin. Recently, high concentrations of relaxin-activated MMP-9 receptors have been found on the acetabular labrum; their expression upregulated by estrogen.

CONCLUSIONS

Menstrual cycle peaks of relaxin activate MMPs, which locally degrade collagen and gelatine. Women have relaxin receptors in multiple joints including the hip and knee, and increased relaxin correlates with increased musculoskeletal injuries. Relaxin has paracrine effects in the female pelvis on ligaments adjacent to hip structures, such as acetabular labral cells which express high levels of relaxin-targeted MMPs. Therefore, it is imperative to investigate the effect of relaxin on the hip to determine if increased levels of relaxin are associated with an increased risk of acetabular labral tears.

Oral contraceptive therapy reduces serum relaxin-2 in elite female athletes

AIM

Recent investigations have demonstrated that athletes with high relaxin-2 levels have a high risk of anterior cruciate ligament injuries, while athletes taking oral contraceptives (OC) have low relaxin-2 levels. It has not yet been clarified whether taking OC reduces relaxin-2 levels. The purpose of this study was to investigate changes in relaxin-2 levels in athletes taking OC.

METHODS

Levels of relaxin-2, estradiol, progesterone, luteinizing hormone and follicle-stimulating hormone were measured in serum samples (n = 183) from 106 elite female athletes. Five athletes with serum relaxin-2 concentrations > 6 pg/mL during the luteal phase were recruited to assess the effect of OC therapy.

RESULTS

Serum relaxin-2 concentrations were significantly higher during the luteal phase (n = 57) than in the follicular phase (n = 72), or in athletes on OC therapy (n = 10) (P < 0.001, P < 0.001 and P < 0.05, respectively). In the luteal phase, 36.8% (21/57) of the athletes had relaxin levels > 6 pg/mL. In 23 athletes, serum relaxin-2 concentrations were measured during both the follicular and luteal phases, revealing that relaxin-2 levels were significantly higher in the luteal phase compared with the follicular phase. In 5 out of 23 athletes, serum relaxin-2 concentrations were > 6 pg/mL in the luteal phase and during the second cycle of OC therapy, relaxin-2 concentrations decreased dramatically to below the detection limit (0.26 pg/mL).

CONCLUSIONS

High serum relaxin-2 concentrations were only detected during the luteal phase. In athletes with high relaxin-2 concentrations during the luteal phase, OC therapy decreased serum relaxin-2 levels.

Percutaneous Reconstruction of the Anterolateral Ligament of the Knee With a Polyester Tape

Recent advances in surgeons' understanding of the anatomic, biomechanical, and radiologic features of the anterolateral ligament (ALL) of the knee have led to an increased interest in reconstruction of this structure as part of the management of knee instability. Even without any technical flaws and proper positioning of the bone tunnels, there is a small subset of patients, approximately 7% of all patients, who experience some residual anterolateral rotational instability after anterior cruciate ligament reconstruction. For this reason, some researchers have turned again toward the anterolateral aspect of the knee and specifically the ALL. In this technical note, the surgical steps for percutaneous reconstruction of ALL of the knee using a polyester tape are described.

The Effect of Phase of Menstrual Cycle on Joint Mobility in the Cervical Spine and Extremities in Nulliparous Women: A Cross-Sectional Study

OBJECTIVE

The purpose of this study was to investigate the range of motion (ROM) of various joints in women throughout the menstrual cycle to determine whether there would be a difference in the ROM between the luteal and follicular phases during extension at the fifth metacarpophalangeal joint and bilateral rotation of the cervical spine in young adult nulliparous women.

METHODS

Sixteen nulliparous women of childbearing age (mean age, 26 years) were recruited from the academic institution where the study was being performed. Participants were randomized into and tested during either the luteal or follicular phases of the menstrual cycle. In the following month, participants were tested in the opposite phases of the menstrual cycle. All testing was performed by a doctor of chiropractic. Differences in ROM were measured in single joint movements (fifth digit hyperextension) and in multijoint movements (bilateral cervical rotation) using an electromagnetic sensor system.

RESULTS

No significant effects of phase were found on peak ROM of the fifth digit or during cervical spine rotation (left, right, or bilaterally), irrespective of trial.

CONCLUSION

There is no difference in ROM of the cervical spine or the fifth metacarpophalangeal joint, regardless of the phase of menses, suggesting there is likely no hormonal influence on these structures during the follicular or luteal phases.

Relationship of relaxin hormone and thumb carpometacarpal joint arthritis

BACKGROUND

The female predominance in thumb carpometacarpal (CMC) joint arthritis has led to speculation that reproductive hormones or hypermobility are responsible. Evidence shows that patients with pathologic laxity have a higher rate of thumb CMC arthritis. Relaxin hormone increases laxity in the pelvic ligaments through upregulation of matrix metalloproteases (MMPs). It is thus a hormone of interest in the development of thumb CMC arthritis.

QUESTIONS/PURPOSES

Our goals were to identify demographic and hormonal factors associated with joint laxity in patients with CMC arthritis and to evaluate the relationship among serum relaxin, relaxin receptors, and MMPs in the anterior oblique ligament (AOL) of the thumb. We hypothesized that serum relaxin was correlated with joint laxity as well as with relaxin receptors and MMPs in the AOL.

METHODS

Forty-nine patients undergoing thumb CMC arthroplasty underwent laxity examination, blood draw, and AOL sampling. Ligaments were analyzed for relaxin receptor and MMPs 1 and 3 using quantitative reverse-transcriptase polymerase chain reaction.

RESULTS

Women demonstrated more joint laxity than men (p < 0.001). RNA analysis confirmed relaxin receptors in the AOL as well as MMPs 1 and 3. There was a significant correlation between serum relaxin and MMP-1 (p = 0.04). Detectable serum relaxin was negatively correlated with relaxin receptors in the AOL (p = 0.02).

CONCLUSIONS

Further studies are needed to evaluate the role of laxity and sex hormones in thumb CMC arthritis.

CLINICAL RELEVANCE

Relaxin hormone may play a role in the development of arthritis at the thumb CMC joint.

LEVEL OF EVIDENCE

Level I, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.

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.

Relationship of serum relaxin to generalized and trapezial-metacarpal joint laxity

PURPOSE

The reproductive hormone relaxin acts to loosen pelvic ligaments in preparation for childbirth and is thought to be a mediator of joint laxity. The purpose of this study was to evaluate the correlation of serum relaxin with radiographic laxity at the trapezial-metacarpal joint and with generalized joint laxity.

METHODS

We enrolled 289 healthy subjects prospectively. Participants completed a demographic questionnaire and were examined for generalized joint hypermobility using the Beighton-Horan scale. Stress radiographs of the trapezial-metacarpal joint were obtained in 163 subjects (56%). Blood samples were collected, and serum relaxin was measured for 287 subjects using enzyme-linked immunosorbent assay for human relaxin-2.

RESULTS

The mean serum relaxin level among all subjects was 1.84 pg/mL (range, 0-45.25 pg/mL). Relaxin was not detectable in 166 of 287 samples, whereas the mean serum relaxin level among the 121 subjects with a detectable relaxin level (of 287 total relaxin samples) was 4.37 pg/mL (range, 0.46-45.25 pg/mL). Mean trapezial-metacarpal subluxation ratio scores were higher among those with a detectable relaxin level compared to those without a detectable relaxin level (0.34 vs 0.30 pg/mL). The average Beighton-Horan laxity score was 1.8 (range, 0-9). There was no correlation between generalized joint laxity measures and serum relaxin levels.

CONCLUSIONS

In a large volunteer population, we demonstrated a relationship between circulating relaxin and trapezial-metacarpal joint laxity. However, we were unable to show a direct link between serum relaxin and generalized joint laxity.

TYPE OF STUDY/LEVEL OF EVIDENCE

Prognostic II.

An extra-articular procedure improves the clinical outcome in anterior cruciate ligament reconstruction with hamstrings in female athletes

PURPOSE

A positive glide is a common finding after ACL reconstructions, especially in women. The aim of this study was to prospectively evaluate the role of Cocker-Arnold's extra-articular procedure in reducing the incidence of a residual postoperative rotational knee laxity.

METHODS

Sixty patients affected by an ACL injury with a +2 (clunk) or +3 (gross shift) pivot-shift test entered this prospective study; they were randomly assigned to group A (control group, hamstrings) or group B (study group, hamstrings plus Cocker-Arnold). Thirty-two patients entered group A and 28 group B. At follow-up, patients underwent clinical evaluation, KT-1000 arthrometer and Lysholm, Tegner, VAS and subjective and objective IKDC form.

RESULTS

At a mean follow-up of 44.6 months, the same expert surgeon reviewed 55 patients (28 group A and 27 group B). The comparison of the results of the evaluation scales used and of the KT-1000 arthrometer did not show statistically significant differences (p>0.05). Lachman test was negative (S/S) in all the patients of both groups (100 %). A residual positive pivot-shift (glide) was found in 16 patients (57.1 %) of group A and in five patients (18.6 %) of group B (p<0.05).

CONCLUSIONS

The extra-articular MacIntosh procedure modified by Cocker-Arnold in combination with ACL reconstruction significantly reduces the rotational instability of the knee.

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.

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.

Relaxin's involvement in extracellular matrix homeostasis

Burgeoning evidence suggests that the hormone relaxin modulates collagen in the extracellular matrix of diverse tissues. In separate lines of study, we provide further substantiation of this hypothesis. Immunofluorescence was used to probe isolated fibroblasts derived from volar oblique ligament explant culture for vimentin, actin, RXFP1, and estrogen receptor beta. Ligaments were obtained as surgical waste from thumb reconstruction patients. Four specimens have been examined to date. Cells derived from these patients expressed vimentin and actin, consistent with fibroblast morphology. Putative fibroblasts derived from two of three female patients expressed RXFP1 receptors; the solitary male was negative. Given the small sample, however, the data are considered preliminary. Immunohistochemistry was used on frozen sections from 26 skin biopsies obtained from children undergoing genitoplasty. A subset of samples was also probed for transforming growth factor (TGF-beta1) and TGF-beta3. Appropriate controls were used. Finally, a subset of patient blood was assayed for relaxin by using an enzyme-linked immunosorbent assay-based method. The results showed RXFP1 receptor expression in the cells that populate the basement membrane in 96% of patients, regardless of gender. Most tissue expressed TGF-beta. Finally, serology suggested that relaxin was detectable in these children. Our two lines of research provide additional evidence for the diverse tissue tropism of relaxin. In particular, connective tissues as diverse as ligaments and basal lamina keratinocytes express RXFP1. These data lend support to our contention that relaxin affects ligament integrity and wound healing.

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.

Ilial anterior rotation hypermobility in a female collegiate tennis player

BACKGROUND AND PURPOSE

This case report describes the examination, evaluation, and intervention by a physical therapist for a female collegiate tennis player with a right ilial anterior rotation hypermobility.

CASE DESCRIPTION

The patient was a 21-year-old, female collegiate tennis player who developed a right anterior ilial rotation hypermobility as a result of her tennis stroke. Functional limitations were related to sitting, squatting, gait, and playing tennis. Treatment interventions consisted of massage, joint manipulation, stretching, stabilization exercises, sport-specific exercises and modification of tennis stroke, proprioceptive taping, and the use of a sacroiliac belt.

OUTCOMES

After 26 weeks (33 treatments), tissue tenderness of the sacroiliac joint region was normalized, pelvic/trunk and lower-extremity mobility and flexibility were restored, sacroiliac symmetry and stability were regained, and the patient achieved her goal of returning to competitive tennis at the collegiate level.

DISCUSSION

The patient's right ilial anterior rotation hypermobility was directly related to the mechanics of her tennis stroke. Her outcomes suggest that rehabilitation should focus on the entire abdomino-sacro-pelvic-hip complex, addressing articular, neural, and muscular inhibitions and deficiencies.

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.

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.

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.

The effects of menstrual cycle on the knee joint position sense: preliminary study

The purpose of this study was to determine the effects of menstrual cycle on proprioception by using the active knee joint position sense test (JPST). The 19 healthy women (ages between 20 years and 27 years) who have normal regular menstrual cycle were included in the study. We applied JPSTs at two different directions throughout the three different phases of the menstrual cycle, i.e. menstrual, follicular, and early luteal in dominant knees. When we started from flexion (90 degrees ), target angles were 70 degrees , 50 degrees , and 30 degrees and we started from extension (0 degrees ), target angles were 20 degrees , 40 degrees and 60 degrees . The absolute reposition errors from the target angles have been evaluated. Results have shown that reposition errors from the target angle at 40 degrees , 50 degrees and 70 degrees of knee angles were higher in the menstrual phase than that of the follicular phase (P<0.05). In addition, higher value of reposition error from the target angle at 40 degrees was found in the menstrual phase compared to luteal phase (P<0.05). In conclusion, we have demonstrated that active JPST was significantly reduced in the menstruation period.

The influence of supplementary tibial fixation on laxity measurements after anterior cruciate ligament reconstruction with hamstring tendons in female patients

BACKGROUND

Female patients undergoing arthroscopic anterior cruciate ligament reconstruction with a hamstring tendon graft developed increased postoperative laxity compared to male and female patients who had reconstruction using a patellar tendon graft. This difference may be due to graft slippage in less dense female tibial bone.

HYPOTHESIS

Reinforcement of tibial fixation of the hamstring tendon graft in women by supplementary methods may reduce laxity.

STUDY DESIGN

Randomized controlled clinical trial; Level of evidence, 2.

METHODS

Fifty-six female patients divided into 2 groups (standard tibial fixation with 7 x 25-mm metal interference screw versus metal interference screw with supplementary staple fixation) were followed for 2 years.

RESULTS

After 2 years, the mean side-to-side difference using KT-1000 arthrometer manual maximum measurements was 1.8 mm (standard group) and 1.1 mm (staple group) (P=.05). The percentage of patients with a side-to-side difference of <3 mm did not differ significantly between the 2 groups (P=.66): 88.8% of the standard group versus 90.5% of the staple group. A grade 0 Lachman test result was present in 63% of the standard group and 86% of the staple group (P=.04). Kneeling pain was experienced by 7% of the standard group and 29% of the staple group (P=.05).

CONCLUSIONS

Supplementary tibial fixation in female patients undergoing anterior cruciate ligament reconstruction with hamstring tendon graft in addition to a single-size screw significantly improves laxity measurements and clinical stability assessment 2 years after surgery. However, this improvement is at the cost of increased kneeling pain.

Knee laxity does not vary with the menstrual cycle, before or after exercise

BACKGROUND

An intriguing explanation for the disproportionately high rate of anterior cruciate ligament injury in female athletes is that the structural properties of the anterior cruciate ligament are affected by the menstrual hormones. Whether this actually occurs, however, is the subject of ongoing debate.

HYPOTHESES

(1) Anterior cruciate ligament laxity is different in the follicular, ovulatory, and luteal phases of the menstrual cycle, and (2) exercise exacerbates the difference in anterior cruciate ligament laxity in the 3 phases.

METHODS

Over the course of 10 weeks, repeated knee laxity measurements were taken on 27 high-level female athletes, before and after exercise. Point in the menstrual cycle was determined with charts of waking temperature and menstruation. The independent effects of menstrual phase and exercise were evaluated using generalized estimating equations.

RESULTS

Data from 18 participants were included in the final analysis. There were no significant differences in anterior cruciate ligament laxity in any of the 3 menstrual phases, before or after exercise.

CONCLUSIONS

Anterior cruciate ligament laxity is not significantly different during the follicular, ovulatory, and luteal phases of the menstrual cycle, and bicycling exercise does not exacerbate or create any differences in anterior cruciate ligament laxity.

Immunohistological detection of relaxin binding to anterior cruciate ligaments

Relaxin, a member of the insulin-like growth factor family, alters collagen metabolism in fibroblasts. It was hypothesized that relaxin interacts with the anterior cruciate ligament (ACL), contributing to its elasticity. Twelve ACL specimens were collected from reconstruction surgeries, sectioned, rinsed, and exposed to rh-relaxin overnight. Polyclonal antirelaxin antibodies, in conjunction with HRP-AEC, localized areas of tissue binding. Controls were used to infer binding specificity. Staining was present in the positive control and all 12 ACL specimens; little or no staining occurred in the negative controls. These data suggest that relaxin binding to the ACL is specific, indicative of a receptor-mediated event.