The quadriceps femoris, or quads, are a group of four muscles located at the front of your thigh. They are the most voluminous muscle of the human body and are some of the largest and strongest muscles in your body. The four muscles that make up the quadriceps femoris are the rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius. The rectus femoris is the only muscle of the quadriceps to cross both the hip and knee joints, and it flexes the thigh at the hip joint and extends at the knee joint. The vastus medialis adducts the thigh and also extends and externally rotates the thigh and stabilizes the kneecap. The quadriceps all work to extend (straighten) the knee. The quadriceps are primarily active in kicking, jumping, cycling, and running.

The quadriceps are vulnerable to injuries, such as contusions (bruising) from blows to the front of your thigh, and quad strains or “pulled quads” can occur. If you want to strengthen your quadriceps, there are several leg exercises you can do, including the squat, leg press, and leg extension.