Observational Study of Growth-Related Knee Pain in Japanese Footballers Aged 12–15 Years: A Subsequent Series Following Children Aged 8–12 Years

This is a subsequent series of studies that examined the factors for growth-related injuries in children aged 8–12 years. We aimed to explore factors associated with growth-related knee pain (GRNP) in Japanese footballers aged 12–15 years. A total of 600 data (200 football players in 7–9th grades) were collected from their parents. Clinical characteristics (age, height, and weight), sports-specific variables (dominant leg, position, and surface), weekly training volume (total days and hours of football), and experience of GRKP (e.g., Osgood–Schlatter disease) within the past 1 year were assessed using a web-based questionnaire. Independent t-tests and chi-square tests were used to investigate the difference between groups with and without GRKP. Logistic regression analyses were also performed to explore risk factors for youth athletes. Additionally, a receiver operating characteristic curve was constructed for the variables used in the logistic regression model. Among junior high school footballers in Japan, 21.0% had experience with GRNP in the past 1 year. Weekly training hours were significantly and positively associated with GRNP (odds ratio, 1.047; 95% confidence interval, 1.016–1.079). The optimal cut-off value for training hours per week was 12.5 h, with low-to-moderate sensitivity (44.4%) and specificity (73.8%). However, clinical and sport-specific characteristics in Japanese footballers aged 12–15 years were not identified as risk factors for recent GRNP. To decrease the risk of GRNP in young Japanese footballers, controlling training volume, which combines adequate recovery or introducing multi-sports events, may be a key strategy for injury prevention.