Rectus femoris is one of the four muscles of quadriceps femoris, a group occupying the front of the thigh. The group consists of rectus femoris, vastus lateralis, vastus medialis and vastus intermedius. Together they straighten the knee; rectus femoris also crosses the hip and helps lift the thigh forwards.
Where is quadriceps femoris located?
Quadriceps femoris occupies the anterior compartment of the thigh: the front region enclosed by fascia, a sheet of connective tissue surrounding muscles. Its muscles lie in front of and beside the femur, the thigh bone. Rectus femoris lies superficially, meaning closer to the skin, with vastus intermedius deep to it, closer to the femur.
Vastus lateralis forms much of the outer thigh, while vastus medialis occupies the inner front of the thigh. Sartorius, a long strap-like muscle, crosses obliquely over the front of the thigh. The adductor muscles, which draw the thigh towards the body's midline, lie mainly on its inner side; the hamstrings lie behind it.
What are the four parts of quadriceps femoris?
The four components are separate muscles that converge into a shared tendon near the knee. A tendon is the strong connective tissue through which a muscle transmits its pull to bone.
| Muscle | Position | Joints crossed |
|---|---|---|
| Rectus femoris | Superficial, central front of the thigh | Hip and knee |
| Vastus lateralis | Outer side of the thigh | Knee |
| Vastus medialis | Inner front of the thigh | Knee |
| Vastus intermedius | Deep to rectus femoris, against the femur | Knee |
The name quadriceps refers to this four-part arrangement. Rectus femoris is therefore one component, not an alternative anatomical name for the whole group. The three vastus muscles arise from the femur, whereas rectus femoris arises from the pelvis.
Where does each quadriceps muscle originate?
An origin is a muscle attachment that usually remains relatively stable during its action. Rectus femoris has a straight head, or separate attachment portion, arising from the anterior inferior iliac spine, a projection on the front of the pelvis. Its reflected head arises from the supra-acetabular groove, a groove above the acetabulum, the socket of the hip joint.
The vastus muscles have broad attachments to the femur:
- Vastus lateralis arises from the greater trochanter, a large upper outer projection of the femur, and the lateral lip of the linea aspera. The linea aspera is a longitudinal ridge on the back of the femoral shaft; its lateral lip is its outer border.
- Vastus medialis arises from the lower part of the intertrochanteric line, a ridge on the front of the upper femur, and the medial lip of the linea aspera, its inner border.
- Vastus intermedius arises from the front and outer surfaces of the femoral shaft, the long central portion of the bone.
The intertrochanteric line is an attachment for vastus medialis, not a standard origin of rectus femoris.
Where does quadriceps femoris insert?
An insertion is the attachment towards which a muscle usually draws the moving structure. The four muscles contribute to the quadriceps tendon, which attaches to the base of patella, the broad upper border of the kneecap.
The patella is a sesamoid bone: a bone embedded within a tendon. Below it, the patellar ligament connects the patella to the tuberosity of the tibia, a prominent attachment area on the front of the shin bone. A ligament joins bones; here, it also continues the force-transmitting pathway from quadriceps femoris to the tibia.
Medial and lateral patellar retinacula, reinforcing bands of connective tissue on either side of the patella, provide additional connections around the front of the knee. These expansions help maintain the patella's alignment as the knee moves.
What does quadriceps femoris do?
Within the muscular system, quadriceps femoris is the principal muscle group responsible for extension of the knee joint. Extension means straightening the knee, moving the leg from a bent position towards a straight one. All four components contribute to this action through their shared tendon and the patellar ligament.
Rectus femoris also produces flexion of the hip joint. Flexion here means bringing the thigh forwards towards the trunk. The vastus muscles cannot perform this action because they do not cross the hip.
Quadriceps femoris can also control knee bending while remaining active. An eccentric contraction is a contraction during which an active muscle lengthens; this allows the group to regulate knee flexion as the body is lowered.
What nerve supplies quadriceps femoris?
All four muscles receive motor innervation from the femoral nerve. Motor innervation means the supply of nerve fibres that activate muscle contraction, linking the muscles to the nervous system. The femoral nerve contains fibres from the second, third and fourth lumbar spinal nerves, which emerge from the lower-back region.
The named supply to rectus femoris is the rectus femoris branch of femoral nerve. Separate muscular branches supply the vastus muscles.
How can you identify quadriceps femoris in the 3D model?
The atlas entry accompanying this article is anchored to rectus femoris, within the zone of quadriceps femoris. This database grouping concerns the wider quadriceps region, but the named muscle is only one of its four components.
Select left rectus femoris or right rectus femoris, then rotate and zoom the model to examine its position along the front of the thigh. You can isolate the selected structure or fade it to compare its position with neighbouring structures. You can also hide selected structures, switch layers or cut a section along the sagittal, coronal or transverse plane.