Which muscle forms the lateral border of the femoral triangle?

The sartorius muscle forms the lateral border of the femoral triangle. This triangular space is clinically significant as it provides access to important structures, including major arteries and nerves in the thigh region. The sartorius is the longest muscle in the human body and runs diagonally across the thigh from the anterior superior iliac spine to the medial side of the tibia.

Understanding the anatomy of the femoral triangle is essential for various procedures, including vascular access and surgery. The boundaries of the triangle are defined by the sartorius muscle laterally, the adductor longus muscle medially, and the inguinal ligament superiorly.

The iliopsoas muscle, while it plays a significant role in hip flexion, lies deeper and does not form part of the lateral border of the femoral triangle. Similarly, the quadriceps femoris, primarily responsible for extending the knee, is located more anteriorly and does not contribute to the formation of this triangle's border. The pectineus muscle is positioned more medially and contributes to the floor of the triangle rather than acting as a border. Thus, the sartorius is uniquely positioned to define the lateral boundary, making it the correct answer.