A 16-year-old girl was complaining of soft swelling on the antero-medial aspect of the Achilles tendon, resembling a soft tissue tumor. She was asymptomatic on normal activity, but running and jumping produced an aching pain. Surgical exploration revealed an accessory soleus muscle and excision resulted in complete relief of the symptoms. J Orthop Sports Phys Ther 1983;5(2):84-85.