Anatomy in detail.
The rectus femoris muscles extend from pelvis to tibia (hip bone to shin bone) at the anterior (front) of the femur (thigh bone)..
rectus ≅ straight
femoris ≅ femur
The rectus femoris muscles cross the hip and knee joints.
When fully engaged the rectus femoris muscles position the legs correctly to the torso.
The rectus femoris are 1 of the 4 muscles in 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 one of the quadriceps that attaches to the pelvis and crosses the hip joint.
The vasti muscles attach to the top of the femur.
The quadriceps are share a common attachment to the tibia via connective tissues (tendon/ligament) that contain the patella (kneecap.
The distal (end furthest from center of body) tendons of these 4 muscles merge to form the common quadriceps tendon above the knee.
The common quadriceps tendon attaches/contains the patella. (pulling kneecaps up)
From the patella the connective tissue continues as the patellar ligament which attaches to the tibial tuberosity of the tibia.
The rectus femoris can be thought of as the lead muscle of the quadriceps.
The pelvic attachments of the rectus femoris muscles 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 have been observed.
Anatomy - A Few More details.
The heads of the rectus femoris merge into an aponeurosis (thin sheet of strong connective tissue), from which the muscle fibres arise as the aponeurosis continues distally (away from the center of the body) on the anterior (front) surface of the muscle.
The lower two-thirds of the posterior (back) surface of the rectus femoris consists of a thick, broad aponeurosis that becomes narrowed into a flattened tendon attached to the patella. This forms the superficial, central part of the common quadriceps tendon.
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