Paul J Read1,2, Jon L Oliver2,3, Mark B A De Ste Croix4, Gregory D Myer5, Rhodri S Lloyd2,3,6. 1. Aspetar Orthopaedic and Sports Medicine Hospital, Doha, Qatar. 2. Youth Physical Development Centre, School of Sport and Health Sciences, Cardiff Metropolitan University, United Kingdom. 3. Sport Performance Research Institute, New Zealand (SPRINZ), AUT University, Auckland. 4. School of Sport and Exercise, University of Gloucestershire, United Kingdom. 5. The SPORT Center, Division of Sports Medicine, Cincinnati Children's Hospital Medical Center, Ohio; Departments of Pediatrics and Orthopaedic Surgery, University of Cincinnati, OH; The Micheli Center for Sports Injury Prevention, Waltham, MA. 6. Centre for Sport Science and Human Performance, Waikato Institute of Technology, New Zealand.
Abstract
CONTEXT: Despite the high frequency of knee injuries in athletes, few researchers have studied the effects of chronologic age and stage of maturation on knee-joint kinematics in male youth soccer players. OBJECTIVE: To use a coach-friendly screening tool to examine knee-valgus scores for players of different ages and at different stages of maturation. DESIGN: Cross-sectional study. SETTING: Academy soccer clubs. PATIENTS OR OTHER PARTICIPANTS: A total of 400 elite male youth soccer players aged 10 to 18 years categorized by chronologic age and stage of maturation based on their years from peak height velocity (PHV). MAIN OUTCOME MEASURE(S): Knee valgus was evaluated during the tuck-jump assessment via 2-dimensional analysis. Frontal-plane projection angles were subjectively classified as minor (<10°), moderate (10°-20°), or severe (>20°), and using these classifications, we scored knee valgus in the tuck jump as 0 ( no valgus), 1 ( minor), 2 ( moderate), or 3 ( severe). RESULTS: A trend toward higher valgus scores was observed in the younger age groups and the pre-PHV group. The lowest frequency of no valgus occurred in the U18 and post-PHV groups. The highest percentages of severe scores were in the U13 and pre-PHV groups for the right limb. Knee-valgus scores were lower for both lower extremities in the U18 group than in all other age groups ( P < .001) except the U16 group. Scores were lower for the post-PHV than the pre-PHV group for the right limb ( P < .001) and both pre-PHV and circa-PHV groups for the left limb ( P < .001). Noteworthy interlimb asymmetries were evident in the U14, U15, and circa-PHV groups. CONCLUSIONS: Reductions in knee valgus with incremental age and during the later stages of maturation indicated that this risk factor was more prevalent in younger players. Interlimb asymmetry may also emerge around the time of the peak growth spurt and early adolescence, potentially increasing the risk of traumatic injury.
CONTEXT: Despite the high frequency of knee injuries in athletes, few researchers have studied the effects of chronologic age and stage of maturation on knee-joint kinematics in male youth soccer players. OBJECTIVE: To use a coach-friendly screening tool to examine knee-valgus scores for players of different ages and at different stages of maturation. DESIGN: Cross-sectional study. SETTING:Academy soccer clubs. PATIENTS OR OTHER PARTICIPANTS: A total of 400 elite male youth soccer players aged 10 to 18 years categorized by chronologic age and stage of maturation based on their years from peak height velocity (PHV). MAIN OUTCOME MEASURE(S): Knee valgus was evaluated during the tuck-jump assessment via 2-dimensional analysis. Frontal-plane projection angles were subjectively classified as minor (<10°), moderate (10°-20°), or severe (>20°), and using these classifications, we scored knee valgus in the tuck jump as 0 ( no valgus), 1 ( minor), 2 ( moderate), or 3 ( severe). RESULTS: A trend toward higher valgus scores was observed in the younger age groups and the pre-PHV group. The lowest frequency of no valgus occurred in the U18 and post-PHV groups. The highest percentages of severe scores were in the U13 and pre-PHV groups for the right limb. Knee-valgus scores were lower for both lower extremities in the U18 group than in all other age groups ( P < .001) except the U16 group. Scores were lower for the post-PHV than the pre-PHV group for the right limb ( P < .001) and both pre-PHV and circa-PHV groups for the left limb ( P < .001). Noteworthy interlimb asymmetries were evident in the U14, U15, and circa-PHV groups. CONCLUSIONS: Reductions in knee valgus with incremental age and during the later stages of maturation indicated that this risk factor was more prevalent in younger players. Interlimb asymmetry may also emerge around the time of the peak growth spurt and early adolescence, potentially increasing the risk of traumatic injury.
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