4. RECTUS FEMORIS

The rectus femoris muscles are located at the anterior (front) of the femur, extending from pelvis to tibia, spanning the hip and knee joints.

rectus ≅ straight

femoris ≅ femur

When fully engaged, the rectus femoris muscles correctly position the legs to the torso, aligning the hip and knee.

rectus femoris keeping it simple

The rectus femoris and the quadriceps femoris.

The rectus femoris is part of the quadriceps femoris muscle group, along with the 3 "vasti" muscles: the vastus lateralis, vastus intermedius and vastus medialis.

Skeleton front off-center view. The left leg shows the rectus femoris muscle from hip to shin. The right leg shows the other 3 muscles of the quadriceps femoris - the vastus medialis, vastus intermedius and vastus lateralis with attach to the top of the femur. The hip joint can be seen on the right leg. The distal tendons of the four muscles merge to form the common tendon of the quadriceps which attaches to and contains the patella. The connective tissue continues as the patellar ligament to the tibial tuberosity. The rectus abdominis muscles are also shown, up the front of the abdomen from pubic symphysis to chest.

The rectus femoris is the only muscle of the quadriceps that attaches to the pelvis. The three vasti attach to the top of the femur.

The rectus femoris can be thought of as the lead muscle of the quadriceps, correctly positioning the legs to the pelvis and aligning the hip and knee.

Proximal attachments of the rectus femoris.

The proximal (closest to the centre of the body) attachments of the rectus femoris are to the pelvis. They are commonly described as "to the ilium of the pelvis via two heads - the straight head and the reflected head" but it is not that simple. Variations in the pelvic attachments of the rectus femoris have been observed.

The tendon of the straight head attaches to the anterior inferior iliac spine.
The rectus femoris may also arise from the anterior superior iliac spine.
The tendon of the reflected head attaches in a groove above the superior rim of the acetabulum and the fibrous capsule of the hip joint. The reflected head may be absent.
A 3rd head may be present, attaching to the ilio-femoral ligament deeply, and superficially to the gluteus minimus tendon as it attaches to femur.

Image showing the possible attachments of the rectus femoris muscles to the pelvis and surrounding tissues. There is some variation between individuals in number and location of the attachments.

Distal attachment of the rectus femoris.

The distal (furthest from the centre of the body) attachment of the rectus femoris is to the anterio-proximal tibia (front, upper shin bone).

The rectus femoris shares this attachment with the 3 vasti muscles and this common attachment is, I think, why these 4 muscles are grouped together as the quaricep femoris.

They attach at the tibial tuberosity of the tibia, via several connective tissue structures which includes the patella (kneecap).

The connective tissues of the rectus femoris's distal attachment are as follows:

Connective tissue fibres from the four muscles of the quadriceps femoris merge into the common tendon of the quadriceps.
The common tendon of the quadriceps attaches to the patella, the largest sesamoid bone (a bone embedded in connective tissue) in the human body.
From the patella, the connective tissue continues as the patellar ligament.
The patellar ligament attaches to the tibial tuberosity of the tibia.

Image showing pelvic bones, femur, tibia and fibula and the rectus femoris muscles. The rectus femoris are pole-likes muscle down the front of the thigh from the ilium of the pelvis (front ridge of the hip bone) to the tibial tuberosity of the tibia (bony lump near the top), attaching via the patellar ligament. The patella/kneecap sits within the ligamentous attachment. The rectus femoris crosses both hip and knee joints so when fully active it positions the leg in the correct position in relation to the rest of the body. Feel for your kneecaps lifting.

The tibial tuberosity is easily palpated as a lump of bone on the tibia below the knee.

Think of the rectus femoris extending upwards from the tibial tuberosity by 'pulling your kneecaps up' and then the muscle being active all the way up to your hip bone. Like a strong pole up the front of each thigh.

The rectus femoris and knee joint.

< section a work in progress >

Articulations of the knee:

Tibiofemoral articulation. This is the weight bearing joint.
Medial and lateral condyles of the femur articulate with the tibial condyles.
Patellofemoral articulation – The posterior surface of the patella is split into medial and lateral facets which articulate with the medial and lateral condyles of the femur. The lateral side - facet and condyle are bigger, restricted lateral movement of the knee.

the patella slides up and down the groove

Positioning/alignment is dependent on the action of muscles and condition of connective tissues.

Trochlear groove "the patellar surface of the femur" patellar groove, intercondylar groove/fossa.

The trochlear surface of the femur is divided into two facets, medial and lateral. Proximally, they are in continuity with a shallow groove conforming to the contours of the distal patellar articular surface. Curving distally and posteriorly, this groove deepens to become the intercondylar notch. external reference will open in new tab

The rectus femoris:

Muscle fibres between two aponeuroses.

The rectus femoris consists of vertically orientated muscles fibres sandwiched between two aponeuroses (strong, thin sheets of connective tissue) at the front and back of the muscle.

The anterior (front) aponeurosis covers the upper portion of the rectus femoris and is created by the tendinous heads (which attach to the pelvis) merging distally on the surface of the muscle.

The posterior (back) aponeurosis covers the lower two-thirds of the rectus femoris and consists of a thick, broad aponeurosis extending up from the kneecap via the superficial, central part of the common quadriceps tendon.

Skeleton seen from the side showing the rectus femoris at the front of the femur from hip to shin, with the patella lying within the ligament/tendon of the muscle. An enlarged schematic picture of the rectus femoris when seen from the side shows the layers of connective tissue known as aponeuroses that sandwich the muscle fibres. A layer of connective tissue from the hip that extends down the front third of the muscle. Another layer at the bottom third at the back of the muscle extending to the patella.