The Rectus Femoris muscle is located at the front part of the thigh and together with the vastus medialis, vastus lateralis and vastus intermedius muscles, form the quadriceps (quad) muscles. The word "rectus" means "straight" in Latin, while the word "femoris" means of the "thigh". As its name suggests, the rectus femoris is the muscle that moves straight along the thigh.
It has two starting points. The first one starts at the bottom of the front part of the hip bone and is known as the straight head. The second one starts just under the straight head at the top of the hip joint, and is known as the reflected head. The two heads move downwards to the thigh coming together and forming one long muscle that continues its way down the thigh, and ends at the kneecap which is known as the patella. The rectus femoris muscle is the only one out of the quad muscles that starts at the hip and works both the hip and knee.
The rectus femoris muscle helps with flexion of the hip and thigh. At the knee it helps with extension. It is an important muscle for everyday tasks such as walking and going up stairs. The rectus femoris is also heavily used in sports which involve kicking movements such as soccer or karate.
It is possible to injure the rectus femoris muscle by overusing the muscle. This usually happens with athletes who participate in sports which involve running, kicking, jumping and cycling. Overuse can cause the muscle to become inflamed or even torn. Pain at the top of the knee or at the thigh close to the hip may indicate an injury to the rectus femoris. Warming up the thigh muscles before the start of the workout is recommended and may help with preventing injury.
Strengthening the muscle could be done in a number of ways, including, leg raises, squats, and step-ups.