The quadriceps femoris, more commonly referred to as the quadriceps or quads, is a group of four muscles at the front of the thigh. Individually, the muscles are called the rectus femoris, the vastus lateralis, the vastus medialis and the vastus intermedius. These muscles come together at the knee via the quadriceps tendon. Tendons are made up of fibrous connective tissue and connect muscles to bones. Ligaments, also made up of fibrous connective tissue, connect bones to bones.
Rectus Femoris Tendons
The rectus femoris is the largest of the quadriceps muscles and is located front and center on the thigh. It is attached to the hip in two places by two tendons, one referred to as the anterior tendon and the other as the posterior tendon. The former is attached to a notch along the front edge of the largest bone of the pelvic girdle, the ilium. The latter is attached along the rim of the socket part of the hip joint, called the acetabulum.
Quadriceps Tendon
At the lower end, near the knee, the tendon of the rectus femoris blends with the tendons of the other three muscles making up the quads to form the quadriceps tendon. The patella, or kneecap, is more or less embedded in this tendon.
Patellar Tendon
The portion of the quadriceps tendon that extends below the kneecap is called either the patellar tendon or the patellar ligament. It is sometimes referred to as a ligament, because it attaches the patella to the tibia--two bones. But because the patella floats within the quadriceps tendon, it doesn't actually function as the lower attachment of the quadriceps muscles. In this scenario, it is considered a tendon, because it attaches the quadriceps to the tibia--muscle to bone.
