Background: Genu varum is a physical deformity marked by bowing of the leg. One of the risk factors of this musculoskeletal alignment is stress on the knee joint such as with exercise. Objectives: Since the evaluation of genu varum has not been widely studies, this study was conducted to examine the association between genu varum and playing soccer. Materials and Methods: Between Septembers 2010-2012, 750 soccer players and 750 non-soccer players 10-18 years of age were included in the study. A questionnaire of data including age, height, weight, body mass index (BMI), years of soccer participation, the average time of playing soccer per week, previous trauma to the lower limbs, history of any fractures of the knee, previous hospitalizations, and the distance of joint lines between the knees was assessed for all subjects. Chi-square, student t-test, and one-way ANOVA were used for statistical analysis by SPSS v.19.0 software. In all tests, a P value of less than 0.05 was construed as statistically significant. Results: Both soccer players and controls had genu varum. However, the incidence of genu varum was higher in the soccer players (P = 0.0001) and it was more prevalent in the 16-18 year age group (P = 0.0001). The results revealed a statistically significant association between the degree of practices and the prevalence of genu varum (P = 0.0001). Moreover, previous trauma to the knees and practicing in load-bearing sports led to an increase in the degree of genu varum (P = 0.0001). Conclusions: There was a higher incidence of genu varum in soccer players than in control adolescents; the stress and load imposed on the knee joint led to more severe genu varum.