Sports related variables including level of physical activity, hours per week of physical activity, number of sports, degree of specialization, and level of competition were significantly associated with reporting knee pain in the previous year.
Knee pain is common among children and adolescents, however the precise incidence is not known. Therefore, the purpose of this study was to establish the prevalence of knee pain in a representative cohort of American children and adolescents 10-18 years old and investigate for any associations with physical activity or sports specialization.
An epidemiological cross-sectional survey was performed in 4,002 American children and adolescents, equally split by age and sex, and representing census-weighted distributions of state of residence, race/ethnicity, and health insurance status. Overall incidence of knee pain (at any time in past year) was calculated, and comparative analyses were performed to investigate for associations with levels of physical activity (number of sports, level of competition, HSS Pedi-FABS activity score, and hours per week) and degree of sports specialization.
After outlier analysis to remove subjects with extremely skewed demographic entries, 3,674 participants were included in demographic reporting. Of the remaining participants that completed the survey, 49.5% were male (n=1,818) and 50.5% were female (n=1,856). The mean age was 14.0±2.5 years and the mean BMI was 21.6±4.4. Most participants (79.3%) participated in at least one sport or physical activity. In total, 25% of participants (n=917) reported experiencing knee pain within the last year.
After outlier analysis to remove subjects with extremely skewed activity data, 3,891 participants were included in activity association analyses. Knee pain was significantly associated with higher physical activity levels based on the HSS Pedi-FABS activity scale (16.4±8.0 vs. 14.0±8.4, p < 0.0001). Participants with knee pain participated in more sports on average (2.1±1.7 vs. 1.7±1.6, p < 0.0001). Specifically, knee pain was reported by 27.5% of participants that were highly specialized (competing in one sport with more weekly hours of training than age in years) and 28.9% of multiple sport athletes compared to 19.3% of participants that played one sport (unspecialized) and 19.1% of participants that did not engage in sports. For the included participants that participate in at least 1 sport (n = 3,026), knee pain was significantly associated with greater hours of weekly physical activity in peak season (12.0±9.0 vs. 10.5±8.6). Additionally, as level of competition increased, the incidence of knee pain significantly increased (p < 0.0001).
The current study quantifies the incidence of knee pain in the previous year in an epidemiologic, census-weighted sample of American children and adolescents. Sports related variables including level of physical activity, hours per week of physical activity, number of sports, degree of specialization, and level of competition were significantly associated with reporting knee pain in the previous year. These results will assist clinicians and researchers in caring for young athletes and designing future research studies.