Design Prospective cohort.

Objectives To compare the incidence of FoAI in high school athletes with low, moderate or high levels of sport specialisation.

Background Sport specialisation has been shown to be associated with increased risk of injuries in high school athletes presenting in clinical settings. However, the association of sport specialisation and incidence of foot or ankle injuries (FoAI) has not been studied prospectively in high school athletes.

Methods Subjects (male and female, grades 9–12) were recruited from 29 Wisconsin high schools during the 2015/16 school year. Specialisation was determined using an established 3 item scale. Athletic trainers reported athletic exposures and FoAI for each subject for each sport season during the entire school year. Multivariate Cox Proportional Hazards Ratios (HR, [95% CI]) were calculated to investigate the association between FoAI and sport specialisation while controlling for sex, sport and previous injury.

Results A total of n=1411 subjects (Female=50%, Age=16.1±1.1 years.) enrolled in the study and participated in 1 59 321 athletic exposures. Subjects were classified as being LOW (59.6%), MOD (26.6%) or HIGH (13.8%) specialisation. One hundred two subjects (7.2%) sustained a FoAI that caused them to miss a median of 7.0 [3.0, 17.2.] days. Injuries were acute (78.6%) or gradual/recurrent (21.4%) onset. Common injuries included ligament sprains (70.9%), muscle/tendon strains (10.3%) and tendonitis/tenosynovitis (8.5%). The incidence of FoAI for MOD subjects was higher than LOW subjects (HR=1.66 [1.01–2.73] p=0.048). The incidence of FoAI for HIGH subjects was higher than LOW subjects (HR=2.12 [1.06–4.26] p=0.034).

Conclusions High school athletes with MOD or HIGH sport specialisation were more likely to sustain a FoAI than athletes with LOW specialisation. Sports medicine providers need to educate parents and interscholastic athletes regarding the increased risk of FoAI for athletes who specialise in a single sport.