Bicipital origin and the course of the plantaris muscle

The plantaris muscle (PM) has a small fusiform muscle belly and a long slender tendon sandwiched between the soleus (SM) and gastrocnemius muscle (GM). During routine dissection for research, an additional PM in the popliteal region of a 75-year-old Korean female was discovered. Two distinct PMs were present, the superior PM (sPM) and inferior PM (iPM). While the sPM originates from the lower lateral supracondylar ridge and the knee capsule, the iPM originates from the femoral condyle and sPM tendon splitting into two parts at the distal belly. The lateral side of the iPM tendon travels between GM and SM and ends at the calcaneal tendon. sPM and the medial side of the iPM tendon run along with the sPM tendon and inserts at the fascia at the inner surface of proximal 1/3 of the medial head of GM. This case report introduces a new variation of the PM that should be taken into consideration.