Accessory soleus muscle. A report of 4 cases and review of literature.

Cadaveric studies have demonstrated the incidence of an accessory soleus muscle ranges from 0.7% to 5.5%. The differential diagnosis of a painful soft tissue mass in the posteromedial region of the ankle includes ganglion, lipoma, hemangioma, synovioma, and sarcomas. In light of these possibilities, most of the early reports of accessory soleus included evaluation and treatment with biopsy, fasciotomy, or excision. Four patients, ranging in age from 14 to 66 years of age at the time of presentation, are discussed. Reports in the literature indicate that accessory soleus is a benign condition, and in most patients, a conservative approach is indicated. In addition, magnetic resonance imaging is the preferred study for the evaluation of this condition. If a diagnosis of accessory soleus is made, and the patient has no symptoms, observation is recommended. However, if the patient has symptoms, fasciotomy generally is a successful form of treatment. For symptoms that persist after fasciotomy, excision of the accessory soleus can be curative.