The 5 Main Muscles of Movement.
Anatomy in detail:
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.
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.
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.
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 rectus femoris shares its distal (furthest from the centre of the body) attachment to the tibia (shin bone) with the other 3 muscles of the quadriceps.
They attach at the tibial tuberosity, located on the proximal, anterior (upper, front) aspect of the tibia, via connective tissue which includes the patella (kneecap).
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 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.