The effects of chronological age and stage of maturation on landing kinematics in elite male youth soccer players

Abstract

Context: Despite the high frequency of knee injuries, there is a paucity of research to show the effects of chronological age and stage of maturation on knee joint kinematics in male youth soccer players.

Objective: To employ a ‘coach friendly’ screening tool to examine knee valgus scores for players of different ages and stage of maturation.

Design: Cross sectional study

Setting: Academy soccer clubs

Patients or other participants: 400 elite male youth soccer players aged between 10-18 years, categorized by chronological age and stage of maturation (pre, circa or post puberty) based on their years from peak height velocity (PHV).

Main outcome measures: Knee valgus was evaluated during the tuck jump assessment via two-dimensional analysis. Participants were subjectively classified as minor (<10°), moderate (10-20°), or severe (>20°) and using these classifications, scored as follows: 0 = no valgus; 1 = minor; 2 = moderate; 3 = severe.

Results: A trend of higher valgus scores were shown in the younger age groups and pre-PHV players. The lowest frequency of “no valgus” were in the U18s and post-PHV players. The highest percentage of “severe” scores were in the U13s. Knee valgus scores were significantly lower in the U18s on both legs than all other age groups (p < 0.001), except for the U16s. Post-PHV players’ scores were significantly lower than pre-PHV youth on the right leg (p <0.001), and both pre- and circa-PHV players on the left leg (p <0.001). Noteworthy inter-limb asymmetries were evident in the U14s, U15s and circa-PHV players.

Conclusions: Reductions in knee valgus with incremental age and during the later stages of maturation indicate that this risk factor is more prevalent in younger players. Inter-limb asymmetry may also emerge around the time of the peak growth spurt and early adolescence, potentially increasing the risk of traumatic injury.