Sex-Specific Changes in Physical Risk Factors for Anterior Cruciate Ligament Injury by Chronological Age and Stages of Growth and Maturation From 8 to 18 Years of Age

Abstract

Objective To critically assess the literature focused on sex-specific trajectories in physical characteristics associated with anterior cruciate ligament (ACL) injury risk by age and maturational stage. Data Sources PubMed, CINAHL, Scopus, and SPORTDiscus databases were searched through December 2021. Study Selection Longitudinal and cross-sectional studies of healthy 8- to 18-year-olds, stratified by sex and age or maturation on ≥1 measure of body composition, lower extremity strength, ACL size, joint laxity, knee-joint geometry, lower extremity alignment, balance, or lower extremity biomechanics were included. Data Extraction Extracted data included study design, participant characteristics, maturational metrics, and outcome measures. We used random-effects meta-analyses to examine sex differences in trajectory over time. For each variable, standardized differences in means between sexes were calculated. Data Synthesis The search yielded 216 primary and 22 secondary articles. Less fat-free mass, leg strength, and power and greater general joint laxity were evident in girls by 8 to 10 years of age and Tanner stage I. Sex differences in body composition, strength, power, general joint laxity, and balance were more evident by 11 to 13 years of age and when transitioning from the prepubertal to pubertal stages. Sex differences in ACL size (smaller in girls), anterior knee laxity and tibiofemoral angle (greater in girls), and higher-risk biomechanics (in girls) were observed at later ages and when transitioning from the pubertal to postpubertal stages. Inconsistent study designs and data reporting limited the number of included studies. Conclusions Critical gaps remain in our knowledge and highlight the need to improve our understanding of the relative timing and tempo of ACL risk factor development.

ACL Research Retreat IX Summary Statement: The Pediatric Athlete, March 17–19, 2022; High Point, North Carolina

“…Evidence was provided for a sequential, sex-specific development of physical risk factors that began with early sex differentiation in the trajectory of body composition, followed by leg strength and power, knee-joint anatomy and laxity, and lower extremity biomechanics. 21 These data clearly showed that body mass index (weight by stature), which has been consistently identified as an independent risk factor for ACL injury, [22][23][24] was a poor representation of body composition during maturation. Although body mass index increased similarly in boys and girls during the pubertal transition, the proportions of the fat mass index and fat-free mass index (FFMI) differed markedly, with boys already having a greater FFMI by age 10, and, by about the age of 13, the fat mass index increased more in girls and the FFMI more in boys.…”

“…27 Despite widespread evidence of bone and tendon adaptations to increases in load, how ligamentous tissue responds to increases in training load or if the training load alone is sufficient to increase this capacity is not widely understood. The ability to positively affect ACL structure through training also has implications for developmental changes in knee-joint laxity, 21,29 an additional risk factor for ACL injury. 23,24 Along with physical risk development, multiple authors and much conversation addressed the role of the central nervous system (CNS) in the ACL injury risk.…”

The Effects of Fatigue on Landing Performance in Young Female Soccer Players

“…Monitoring the execution technique of certain sportspecific skills such as stopping or landing takes on a strong relevance in the young athlete training, especially if the athlete is a young female soccer player. In fact, the literature points out that age and gender are two factors that condition lower limb motion patterns between 11-16 years old (Shultz et al, 2022;Otsuki et al, 2021;Yu et al, 2005). Comparison of values obtained in the LESS under resting conditions and post functional agility short-term fatigue protocol showed a statistically significant decrease in landing technique in young female soccer players with a large ES.…”

Anterior knee laxity is greater in athletic females who attain menarche at a younger age

“…Greater oestrogen exposure at an earlier age may also accelerate growth plate closure [19,31] and retard musculoskeletal growth [10] in mid-to late pubertal girls, as males continue to accrue muscle mass [33]. This may have implications for anterior knee laxity, as ACL development (which is negatively correlated with anterior knee laxity) is positively correlated with height [13] and thigh muscle mass [23], and both height and thigh muscle mass plateau about the same time as ACL size during female adolescent growth [22]. Consistent with these findings, MA 9-11 and MA 12 females in our study were of somewhat smaller stature than MA 14+ despite being of similar ages.…”