The muscle group at the front of the thigh, made up of four muscles, is called the quadriceps. The name comes from the Latin roots for “four” and “headed,” reflecting the group’s four-part structure.
The quadriceps femoris consists of the rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius. Together, these muscles occupy the front of the thigh and converge into the quadriceps tendon, which attaches to the patella, or kneecap. The force continues through the patellar ligament to the tibia.
Their primary action is extending the knee, which is essential for standing up, walking, running, kicking, and climbing stairs. The rectus femoris also helps flex the hip because it crosses both the hip and knee joints.
A common mix-up is confusing the quadriceps with the hamstrings. The quadriceps are on the front of the thigh and straighten the knee; the hamstrings are at the back and help bend the knee. The vastus medialis is sometimes discussed separately in relation to kneecap tracking, but it remains one part of the quadriceps group.