Abstract Background and Aim Duchenne muscular dystrophy (DMD) is the most common muscular dystrophy of childhood and affects 1 per 3600 male births. Electromyography and muscle biopsy were a commonly ordered invasive diagnostic procedure, used to evaluate children with weakness suspected to be caused by muscle disease. Recently, neuromuscular imaging is used as non-invasive diagnostic tool for various muscle diseases. Muscle ultrasonography is increasingly used for the diagnosis and follow up of children with DMD. Aim of the Work The aim of this study was to describe the pattern of ultrasonographic thigh muscles involvement, and to correlate the US findings with motor functional status. Patients and Methods Functional motor assessment was the functional performance protocol (GSGC score) Gait (G), Climbing stairs (S), Gower's maneuver (G), and Arising from a chair (C). Sonographic assessment of quadriceps rectus femoris muscles. Results Twenty-four genetically confirmed ambulatory DMD children were enrolled in this cross- sectional study. Their mean age of 7.46 ± 1.82 (4.5–11 years). The Rt and Lt Quadriceps muscles positively correlated with the age. The Rt. and Lt. Quadriceps muscle assessment significantly related to the scores for gait, stairs, chair arising, GSGC total score, time to walk 10 m, Time to rise from the floor. Conclusion Ultrasonography could be used as a non-invasive method to assess progressive muscle hypertrophy in boys with Duchenne muscular dystrophy. Furthermore, Quadriceps muscle US correlates with the motor functions in ambulant DMD boys below the age of 12 years.