Insertion of which muscle occurs at the medial surface of the tibia?

The sartorius muscle is uniquely positioned in the anterior compartment of the thigh. It originates from the anterior superior iliac spine (ASIS) and travels down, crossing the thigh, before inserting on the medial surface of the tibia via the pes anserinus. This anatomical routing allows the sartorius to flex, abduct, and laterally rotate the hip, as well as flex the knee. Its insertion location is significant as it highlights the muscle's role in movements that involve bending the knee and performing activities such as sitting cross-legged.

Other muscles listed, like the rectus femoris and vastus lateralis, are primarily involved in knee extension and have their insertions at the patella or the quadriceps tendon, making them unsuitable for this question's criteria. The biceps femoris, part of the hamstrings, inserts laterally on the fibula rather than medially on the tibia, which further confirms why the sartorius is the correct response. Thus, understanding the anatomy and functions of the sartorius, along with its unique insertion point, clarifies why it is the correct choice.