Quadriceps

The quadriceps femoris muscle (ˈkwɒdrᵻsɛps_ˈfɛmərᵻs, also called the quadriceps extensor, quadriceps or quads) is a large muscle group that includes the four prevailing muscles on the front of the thigh. It is the sole extensor muscle of the knee, forming a large fleshy mass which covers the front and sides of the femur. The name derives . The quadriceps femoris muscle is subdivided into four separate muscles (the 'heads'), with the first superficial to the other three over the femur (from the trochanters to the condyles): The rectus femoris muscle occupies the middle of the thigh, covering most of the other three quadriceps muscles. It originates on the ilium. It is named for its straight course. The vastus lateralis muscle is on the lateral side of the femur (i.e. on the outer side of the thigh). The vastus medialis muscle is on the medial side of the femur (i.e. on the inner part thigh). The vastus intermedius muscle lies between vastus lateralis and vastus medialis on the front of the femur (i.e. on the top or front of the thigh), but deep to the rectus femoris muscle. Typically, it cannot be seen without dissection of the rectus femoris. The rectus femoris arises from the anterior inferior iliac spine and from the superior edge of the acetabulum. It is thus a biarticular muscle. The other parts of the quadriceps arise from the surface of the femur. All four parts of the quadriceps muscle ultimately insert into the tuberosity of the tibia via the patella, where the quadriceps tendon becomes the patellar ligament. There is a small fifth muscle of the quadriceps complex — the articularis genus muscle — that is not often included. In addition, cadaver studies have confirmed the presence of a sixth muscle, the tensor vastus intermedius. While this muscle has a variable presentation, it consistently originates at the proximal femur, runs between the vastus lateralis and vastus intermedius muscles, and inserts distally at the medial aspect of the patellar base.