Relationship Between Age at Adult Height and Knee Mechanics During a Drop Vertical Jump in Men

BACKGROUND: Anterior cruciate ligament (ACL) injuries are relatively common among younger athletes, with significant physical, psychological, and financial consequences. Research has largely focused on female athletes by identifying specific risk factors for an ACL injury, including variation in pubertal growth timing. There is less known about risk factors in males, and little is known about the effects of pubertal development on ACL injury risk in men. PURPOSE/HYPOTHESIS: The purpose of this study was to analyze the relationship between an indicator of pubertal growth timing (age at adult height) and biomechanical risk for ACL injuries in men. We hypothesized that earlier age at adult height is correlated with riskier landing biomechanics during a drop vertical jump (DVJ) in men. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: A total of 21 recreationally active male students (age range, 20-33 years) were included. Participants completed a questionnaire on age at adult height and limb dominance, and anthropometric measurements were taken. There were 6 DVJ tests performed, with participants landing on a force plate while digital cameras recorded kinematic data from retroreflective markers placed according to the Helen Hayes marker system. Primary outcomes were sagittal and frontal plane knee kinematics and kinetics during contact. Data were analyzed using Pearson product-moment correlation. RESULTS: In both limbs, age at achieving adult height was significantly negatively correlated with knee flexion/extension angle at toe-off (dominant: r = –0.79, P < .01; nondominant: r = –0.74, P < .01) and with peak flexion (dominant: r = –0.63, P < .01; nondominant: r = –0.70, P < .01) and extension (dominant: r = –0.66, P < .01; nondominant: r = –0.56, P = .01) angles during contact. In the nondominant limb, age at adult height was significantly negatively correlated with varus/valgus angle at initial contact (r = –0.43; P = .05) and toe-off (r = –0.44; P = .04) and was positively correlated with peak varus moment during contact (r = 0.42; P = .06). Age at adult height was also positively correlated with peak vertical ground-reaction force (r = 0.58; P < .01). CONCLUSION: Later age at adult height was correlated with riskier landing profiles in this study. This suggests that males with later or longer pubertal growth may have increased mechanical risk for ACL injuries. A better understanding of the effects of pubertal growth on landing biomechanics can improve the early identification of male athletes at greater risk for injuries.