Anatomy
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What is the Rectus Femoris?

Alex Paul
Alex Paul

The rectus femoris is one of the four muscles that make up the quadriceps group. Its primary functions are to flex the hip and extend the knee, making this an important muscle for a number of activities that require movement of the lower body. The muscle is located in the center of the thigh and runs from the bottom of the spine down to the kneecap. Only the sartorius muscle is also included in the quadriceps group and is involved in both hip and knee movement.

The rectus femoris has two origins. The first is the anterior origin and occurs at the bottom of the spine. There is also the posterior origin at the acetabulum. Both of these start with a tendon and come together before running down to the thigh to where the muscle fibers begin. The insertion of the muscle is via a tendon known as the quadriceps tendon, which connects into the patella.

Sprinters and other athletes who frequently overuse their muscles are at risk for rupturing a rectus femoris tendon.
Sprinters and other athletes who frequently overuse their muscles are at risk for rupturing a rectus femoris tendon.

Extending the knee is one of the main jobs of the rectus femoris muscle. This muscle, however, becomes weaker in relation to hip flexion when the knee is extended because it becomes shortened, meaning it cannot work as well. For this reason when the rectus femoris is shortened other muscles are more involved in hip flexion.

In a similar way the muscle is also weaker in knee extension when there is already hip flexion. Again, this is because the muscle is placed in a shortened state and cannot provide the same level of force. In this situation, knee extension is achieved through other muscles in the quadriceps groups.

The rectus femoris is one of the four muscles that make up the quadriceps group.
The rectus femoris is one of the four muscles that make up the quadriceps group.

The three other main muscles in the quadriceps muscle group are the vastus lateralis, vastus intermedius and vastus medialis. All of these muscles assist in keeping the patella stable while extending the knee. For this reason they are all essential to basic activities such as walking or running. The rectus femoris is the most central of the muscles and is named due the way it reaches straight down the front of the thigh.

Side lunges strengthen and tone the thighs -- including the rectus femoris -- and other leg muscles.
Side lunges strengthen and tone the thighs -- including the rectus femoris -- and other leg muscles.

If this muscle becomes ruptured, it becomes a serious and painful injury. Often a rectus femoris tendon rupture occurs through repeated overuse of the muscle during actions such as kicking or sprinting. Symptoms include a sharp pain in the hip or groin along with bruising and sometimes swelling. The area will also usually be painful to touch.

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    • Sprinters and other athletes who frequently overuse their muscles are at risk for rupturing a rectus femoris tendon.
      By: Valeriy Velikov
      Sprinters and other athletes who frequently overuse their muscles are at risk for rupturing a rectus femoris tendon.
    • The rectus femoris is one of the four muscles that make up the quadriceps group.
      By: Dirima
      The rectus femoris is one of the four muscles that make up the quadriceps group.
    • Side lunges strengthen and tone the thighs -- including the rectus femoris -- and other leg muscles.
      By: z3zo
      Side lunges strengthen and tone the thighs -- including the rectus femoris -- and other leg muscles.
    • A ruptured rectus femoris may necessitate physical therapy.
      By: WavebreakmediaMicro
      A ruptured rectus femoris may necessitate physical therapy.
    • One of the rectus femoris' points of origin is at the bottom of the spine.
      By: pankajstock123
      One of the rectus femoris' points of origin is at the bottom of the spine.
    • The rectus femoris can be strengthened through leg extensions.
      By: CandyBox Images
      The rectus femoris can be strengthened through leg extensions.
    • Extending the knee is one of the main jobs of the rectus femoris muscle.
      By: high_resolution
      Extending the knee is one of the main jobs of the rectus femoris muscle.