Accessory soleus presenting as a posterior ankle mass: a case report and literature review.

The accessory soleus muscle is a rare anatomic variant that may present as a mass in the posterior-medial aspect of the ankle in young adults. The presence of such a mass may result in pain and difficulty with running. We present a case of accessory soleus muscle in a 21-year-old soldier and review the literature. We present the first magnetic resonance imaging studies in the American literature, to our knowledge, of this unusual anomaly.