The subject of this research is the angular deformity of the knee joint of younger adolescents. The aim of the research was to measure the frequency, structure and size of static disorders of the knee joint in the frontal plane, depending on sex and calendar age. The sample comprised 251 respondents, primary school pupils, 10, 12 and 14 years of age. This is one of the most sensitive periods in the development of young pupils. It is characterized by a sudden change in the dynamics of living and also by an increased occurrence of postural disorders (Radisavljević, 2001; Kosinac, 2005). To estimate the status of the knee joint, we selected two variables: X-shaped legs (Genua valga) and O-shaped legs (Genua vara). Variables for estimating the status and structure of existing deformities were subjected to the somatoscopy method and to the test of 'voluntary' muscle contraction (Radisavljević, 2001; Jovović, 1999). The greatest angular frequency of knee joint disorders is at the age of 12 for girls and at the age of 14 for boys. O-shaped legs are present in a slightly higher percentage in both sexes and all three age groups. The greatest frequencies of deviations from normal are functional disorders, which can be successfully corrected in a large extent by using active and passive measures.
