The quadriceps muscle, or quadriceps femoris, is actually a group of four muscles in the front and side of the thigh. Individually, these four thigh muscles are known as rectus femoris, vastus medialis, vastus intermedius and vastus lateralis. They are involved in extending, or straightening, the knee, and rectus femoris also lifts the thigh at the hip. A well-toned quadriceps muscle helps to strengthen and stabilize the knee.
Rectus femoris, situated right at the front of the thigh, runs from the hip bone to the tibia, or shin bone. A strong strap of tissue, called the quadriceps tendon, attaches the rectus femoris, together with the other quadriceps muscles, to the tibia. The patella, or knee bone, is situated within the quadriceps tendon.
Vastus lateralis is positioned on the outside of the thigh, and vastus medialis is on the inside of, and behind, rectus femoris. The vastus intermedius muscle is situated beneath the other muscles. All of the vastus muscles are attached to the thigh bone, or femur, above and the quadriceps tendon below.
Contusions are the most common form of quadriceps muscle injury, and the rectus femoris is most often affected. A contusion is an area of bruising caused by a direct blow, which could occur during sporting activities. Muscle damage, inflammation and bleeding lead to symptoms of swelling and tenderness, and it may be difficult to walk or bend the knee.
Strains of the quadriceps muscle most commonly occur in athletes who repeatedly carry out kicking, jumping and sprinting actions. The rectus femoris travels across both the hip and knee joints and is more frequently damaged than the vastus muscles, with the typical site of injury being just above its attachment to the patella, or knee bone. Varying degrees of muscle strains can occur, ranging from a tiny amount of tearing to a complete rupture. Symptoms can also vary, from mild discomfort in the thigh to severe pain, swelling and difficulty walking.
Contusions and sprains are managed by bending the knee as far as possible to help prevent bleeding and to stop the muscle fibers from shortening as they begin to heal. Ice and compression bandages are applied and, after 24 hours, the leg is elevated and rested. Stretching exercises may be carried out several times a day to prevent scar tissue from shortening the muscle. If a quadriceps muscle ruptures completely, surgery may be necessary. Recovery times vary according to the severity of the injury, from a few days to several months.