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Objectives and questions: To assess differences in anterior tibial translation (ATT) measured with Genourob^® (GNRB) in pre-pubertal versus adolescent patients, and to update the 1988 established reference values by Baxter et al. using the more precise 200 N measurement protocol.

Material and methods: This retrospective observational study analyzed prospectively collected registry data from 258 patients (142 male, 116 female) aged 10–18 years. The primary measurements of the uninjured contralateral knees were included, with patients under annual follow-up after ACL injury to the opposite knee. Objective GNRB measurements of ATT were performed at 20° of knee flexion under 200 N loading. Demographic data included sex, age, height, weight, and BMI. Normality of continuous variables was assessed using the Shapiro–Wilk test, and descriptive statistics are reported as mean ± SD.

Results: Of the 258 patients, 55% were male. Injuries were evenly distributed between left (48%) and right (52%) knees. The mean ATT at 200 N in the uninjured knees was 5.0 ± 1.2 mm (n=258). It decreased from 6.8 ± 1.4 mm in patients aged 10–13 years to 4.8 ± 1.2 mm in those aged 18 years (p = 1.48 × 10⁻⁵). A significant negative correlation was observed between ATT at 200 N and age (r = –0.31, p < 0.001), as well as for height (r = –0.23) and weight (r = –0.37).

Discussion and conclusions: This analysis provides a comprehensive overview of the evolution of physiologic anteroposterior knee laxity in a cohort of pediatric and adolescent patients with contralateral ACL injuries. It allows for an objective assessment of the capsuloligamentous maturation process in this age group and may help to improve the understanding of dramatic rise of ACL injuries in adolescents. In establishing precise, age-dependent reference values for paediatric knees, this study assists in monitoring paediatric patients with knee injuries and in guiding treatment decisions regarding ATT before decompensation of the knee and further concomitant injuries occur. By providing robust, contemporary data, this study paves the way for evidence-based treatment strategies and future guideline development.