The onset and timing of the growth of children and adolescents occurs with considerable variability in cohorts of the same chronological age. The musculoskeletal system changes in proportion over time, and lever-arm changes, altered individual flexibility, and strength lead to age-specific injury patterns in youth sports. In sports, juniors are commonly grouped according to their chronological age. Early- and late-maturing children and adolescents might therefore not routinely be trained in relation to their biology. This not only represents a risk for overuse and injury but might limit their development in sports. To obtain information about the biological age of children is challenging. Numerous methods have been studied and validated. However; the implementation of these methods on a large scale is still to come. This report provides a brief overview of growth dynamics in relation to youth sports injuries and describes a few challenges for the future.