The aim of this study is to evaluate different aspects of mental stress aspects and its role as a potential risk factor for traumatic knee injury in youth athletes. Approximately 300 athletes (age 16-19) 50% women) who are involved in high risk sports (soccer, handball and floorball) will be included. The athletes will record his/hers traumatic knee injury together with information about training regimes and some details on injury mechanism on a web-based form. The form also includes questions about mental stressors, such as club exchange, changed game system in addition to conflict within and outside the family, etc, prior to injury.

The present study will contribute new knowledge on levels of muscle function and different aspects of mental stress factors that may be related to traumatic knee injury in young athletes.

Inclusion Criteria:

Male and female sport high school athletes Aged 15-19 years Participating and competing in soccer, handball, or floorball

Exclusion Criteria:

Traumatic knee injury prior to sport high school.

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Coaches of approximately 1400 athletes, aged 16-19 years, involved in sports related to high risk of knee injury (soccer, handball and floorball), at 70 high schools in Sweden, will be contacted and introduced to the study through email. The team coach at each school will distribute a web-based form to the athletes during their first, second or third year of the high-school period by email or through the school's intra-net system.

We estimate that approximately 300 youth athletes (50% women) will be included. From the included participants, ahtletes with traumatic knee injury will be included for furhter analysis.