Introduction: Genu varum and genu valgum deformities are highly prevalent in Iran. These deformities bring about changes in the structure and function of muscles around the knees. The aim of the present investigation was to study the structure of medial and lateral gastrocnemius muscles in patients with primary genu varum and genu valgum deformities and individuals with normal knee alignment, using rehabilitative ultrasound imaging. Method and Materials: : A Honda 2100 (Honda Co., Japan) real time ultrasound scanner was used in the current the study. The dominant legs of 18 women, 6 with genu varum (mean age: 22.00±1.78 years), 6 with genu valgum (mean age: 21.67±1.03 years), and 6 with normal alignment (mean age: 21.83±1.72 years) were examined. The morphological parameters like muscle thickness, pennation angle and fascicle length of medial and lateral gastrocnemius muscle were compared among groups. Results: In participants with genu varum, the medial gastrocnemius was thinner, closer and shorter in terms of muscle thickness, pennation angle, and fascicle lengths when compared to the lateral gastrocnemius (P<0.05). However, in participants with genu valgum, it was the other way around (P<0.05). In participants with normal alignment, there was no statistically significant difference between the medial and lateral gastrocnemius muscle structures. Conclusions: The rehabilitative ultrasound imaging is highly recommended for studying the structure of gastrocnemius muscle. The structural differences between medial and lateral gastrocnemius muscles may be due to the long term neuromuscular adaptation to knee joint alignment in both genu varum and genu valgum deformities.Key words: Genu, Valgum, Varum, Rehabilitative, Ultrasound, Imagin
