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Weaker lower extremity muscle strength predicts traumatic knee injury in youth female but not male athletes
  1. Sofia Ryman Augustsson,
  2. Eva Ageberg
  1. Department of Health Sciences, Musculoskeletal Function, Lund University, Lund, Sweden
  1. Correspondence to Dr Sofia Ryman Augustsson; sofia.ryman_augustsson{at}


Background The role of lower extremity (LE) muscle strength for predicting traumatic knee injury in youth athletes is largely unknown.

Aims The aim was to investigate the influence of LE muscle strength on traumatic knee injury in youth female and male athletes.

Methods 225 athletes (40% females) from sport senior high schools in Sweden were included in this case–control study. The athletes recorded any traumatic knee injury that had occurred during their high-school period in a web-based injury form. A one repetition maximum (1RM) barbell squat test was used to measure LE muscle strength. The 1RM was dichotomised to analyse ‘weak’ versus ‘strong’ athletes according to the median (weakmedian vs strongmedian).

Results 63 traumatic knee injuries, including 18 ACL injuries, were registered. The majority of injured female athletes were in the weak group compared with the strong group (p=0.0001). The odds of sustaining a traumatic knee injury and an ACL injury was 9.5 times higher and 7 times higher, respectively, in the weakmedian group compared with the strongmedian group in females (p ≤0.011). A relative 1RM squat ≤1.05 kg (105% of bodyweight) was established as the best cut-off value to distinguish high versus low risk of injury in female athletes. No strength–injury relationships were observed for the male athletes (p ≥0.348).

Conclusions Weaker LE muscle strength predicted traumatic knee injury in youth female athletes, but not in males. This suggests that LE muscle strength should be included in injury screening in youth female athletes.

  • muscle strength
  • youth athletes
  • traumatic knee injury
  • ACL

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  • Acknowledgements The authors thank the contact persons at the national sport programmes for distributing the injury form and for providing muscle strength data. The authors also like to thank Tommy Schyman for his valuable guidance with the statistics.

  • Contributors SRA and EA were responsible for the planning, conception and design of the study. SRA was responsible for data collection and data analyses. Both authors were involved in the interpretation of the data and in manuscript writing, and approved the final version.

  • Funding This study was supported by grants from Swedish Research Council for Sport Science, the Free Professional Support Fund from The Swedish Association of Physiotherapists, the Crafoord foundation, and the Faculty of Medicine Lund University.

  • Competing interests None declared.

  • Ethics approval The study was approved by the Ethics Committee at the University of Gothenburg, Sweden (EPN no 929-13).

  • Provenance and peer review Not commissioned; internally peer reviewed.