Corpus: Rectus femoris muscle
from Latin: rectus - right, straight
1. Definition
The rectus femoris muscle is a thigh muscle that forms part of the quadriceps femoris muscle.
2. Anatomy
2.1. Origin
The rectus femoris muscle has two heads. The straight head originates from the anterior inferior iliac spine. The reflected head is highly variable and originates from the upper edge of the acetabulum in the supraacetabular sulcus. Both tendons of origin unite at an acute angle, with their fibers extending into the aponeurosis on the front of the muscle, which serves as an anchor for other muscle fibers.
2.2. Attachment
The attachment tendon of the rectus femoris muscle begins as a continuation of its distal aponeurosis about ten centimeters proximal to the kneecap. It attaches to the upper pole of the patella and extends as the patellar ligament from the lower pole of the patella to the tibial tuberosity.
2.3. Innervation
The rectus femoris muscle is innervated by the femoral nerve (L2-L4), with predominant contributions from the L4 spinal segment.
3. Function
The rectus femoris muscle is the only part of the quadriceps femoris muscle that is bi-articular, meaning it acts on both the knee and hip joints. In the knee joint, it causes extension (straightening). In the hip joint, it triggers flexion (bending). Its force on the hip joint is greater when the knee is bent than when the leg is extended.
4. Clinic
Fiber tears of the rectus femoris muscle or its tendons are relatively common sports injuries. The muscle can be partially or completely torn, often occurring in football due to sudden sprints, jumps, or kicks. These injuries are characterized by pain and swelling along the course of the muscle.