A unique case of an accessory sartorius muscle.

The sartorius muscle (SM) is a long strap muscle originating from the anterior superior iliac spine and inserting onto the medial surface of the proximal tibia. It crosses the anterior compartment of the thigh obliquely and descends towards the medial aspect of the knee. We found an accessory sartorius muscle (ASM) from the inguinal ligament and an original SM bifurcated into medial and lateral heads. The ASM merged with the medial head of the SM and inserted on the medial aspect of the tibia as the pes anserinus. The lateral head of the SM continued inferiorly and inserted on the medial aspect of the patella. We report a unique variation in the morphology of the SM, and discuss its functional and clinical implications.