Obturator Externus is a fan-shaped muscle being located above and lateral to the pectineus. It’s not a muscle of adductor compartment but its here due to its close relationship with the structures of the adductor compartment of the thigh.
It originates from the outer surface of the anterior half of the obturator membrane and adjoining anterior and inferior margins of the obturator foramen.
The fibres converge backwards and laterally to create a tendon, which spirals upward over the inferior and posterior surfaces of the neck of femur to be fit in the trochanteric fossa of greater trochanter of the femur.
By the posterior section of the obturator nerve.
It’s the lateral rotator of the thigh.