Rupture of the rectus femoris at the musculotendinous junction is very rarely reported in the literature, especially which is caused by chronic repetitive stimulation. A 21 year old soldier complained of progressing right thigh pain and mass for 8 weeks after military training. MRI of the right thigh showed inhomogenous mass lesion suspecting soft tissue tumor. However ultrasonographic examination showed torn retracted rectus femoris tendon at musculotendinous junction. One year after primary repair of ruptured tendon, the patient is free from symptoms and returned to full previous activities. Knowledge of this sonographic and MRI finding will help the surgeon to diagnose and treat this rare injury.