Background Karate is a popular combat semi-contact sport among juniors, but there are only few studies available on the epidemiology of injuries in karate junior athletes.

Aim The aims of this study were to determine the incidence and pattern of injuries in top-level karate competition for athletes aged 16 to 20 years, and to compare injury rates between age groups (ie, under 18-year-old [U18] and under 21-year-old [U21]) and genders, following the introduction of new weight categories.

Methods A prospective injury surveillance was undertaken at four consecutive World Karate Championships (2009 to 2015), following the same protocols used in previous investigations.

Results During the four championships, a total of 257 injuries were recorded, with an incidence of 41.4/1,000 athlete exposures (AEs, 95% CI 36.4 to 46.3). The injury rate was significantly lower for females with a rate ratio 0.63 (95% CI 0.48 to 0.82). Most of the injuries were minor ones: contusions (n=100), followed by abrasions (n=63) and epistaxis (n=62). Only 10% of the injuries were time-loss injuries (injury incidence rates 4.2/1,000 AEs; 95% CI 2.7 to 6.1). Face injuries represented 69.6% of the injuries, most of them were minor ones (light abrasions 24.5%, epistaxis 24.1%, contusion 16.7%). Change of rules (raising the number of weight categories from three to five) reduced injury incidence in the U21 category.

Conclusions The total injury rate in junior competitions is lower compared with elite adult athletes and higher compared with younger elite athletes. Time-loss injuries are rare. The implementation of the new competition categories in U21 karate has been associated with a significant reduction in injury rate.