The report on the co-occurrence of two different rare anatomic variations of the plantaris muscle tendon on both sides of an individual.

The plantaris muscle usually begins with a short and small muscle belly on the popliteal surface of the femur and on the knee joint capsule. It continues distally to form a long and thin tendon typically fixed to the calcaneal tuberosity. However, the course and the insertion of the plantaris muscle is variable, which may influence the development of Achilles tendinopathy. The plantaris tendon may also be used for reconstruction of tendons and ligaments, such as talofibular and calcaneofibular ligament. In literature review no data concerning the co-occurrence of anatomic variations of the plantaris muscle tendon in different individuals has been found. This report presents a rare variant of the plantaris muscle insertion into the deep crural fascia on the left leg and absence of the plantaris muscle on the right leg of the same individual.