A young male presented with a diffuse painless bulge on the posterior medial aspect of right distal third leg and ankle region. Ultrasound was done to localize and evaluate the bulge. Ultrasound shows a muscle with normal echopattern between Achilles tendon and flexure hallucis longus tendon; which inserts through a short tendon at the upper surface of the calcaneum. There is no such muscle in the asymptomatic left leg-ankle region. Findings favor an accessory soleus muscle which is unilateral.