An unusual accessory soleus muscle with its clinical implications

Anomalous, supernumerary or accessory muscles in the flexor compartment of the leg are reported in the medical literature. The accessory soleus muscle is one of the variations found in this region, with the incidence ranging from 0.7-5.5%. The presence of an accessory muscle in the posterior compartment is of clinical significance, as it can be mistaken for a tumor during the clinical examination, or it can lead to the compression of surrounding neurovascular structures. During routine dissection of a cadaver, an accessory muscle was found in the medial aspect of the middle portion of the posterior compartment of the left leg. It originated with two heads from the middle portion of the soleus muscle and got inserted onto the medial surface of the calcaneum. The muscle was unilateral and was supplied by the tibial nerve. Evidence about these accessory muscles and their location and attachments are useful in making a proper diagnosis and management.