The quadriceps
The quadriceps on the front of the thigh has four heads. The rectus femoris starts on the hip bone above the hip joint. The vastus lateralis, the vastus medialis and, beneath them, the vastus intermedius start on the femur. Together they are among the largest and strongest muscles in the body.
Muscles of the hip and thigh from the front and from behind, among them the quadriceps, the sartorius, the adductors and the hamstrings, OpenStax Anatomy and PhysiologyWikimedia Commons, OpenStax, CC BY 4.0 (1122 Gluteal Muscles that Move the Femur.jpg)
The four join in one tendon that encloses the patella and continues as the patellar ligament to the tibia below the knee. The patella holds the tendon away from the joint, which gives the muscle more leverage. The quadriceps straightens the knee in standing up, climbing, jumping and kicking.
The rectus femoris crosses both the hip and the knee, so it also bends the hip. The quadriceps is supplied by the femoral nerve, from the second to fourth lumbar segments. A tap on the patellar ligament stretches the muscle and makes it twitch, the knee-jerk reflex.
Sources
- Susan Standring (ed.), Gray's Anatomy, 42nd ed. (2020), chapters on the pelvic girdle, gluteal region and thigh and on the knee.
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