The Obturator externus (OE) muscle originated from the external bony margin of the obturator foramen in clockwise direction from 12 o'clock around to the 10 o'clock position (right hip viewed from the front) and a few fibres arose from the obturator membrane.
It formed a musculo-tendinous junction at the level of femoral neck. The fibres passed laterally along the inferior margin of the acetabulum acting like a sling at the inferior part of the neck. The muscle inserted as a cylindrical tendon into the trochanteric fossa with some fibres extending towards the piriformis fossa. 
the posterior branch of the obturator nerve
obturator and medial circumflex femoral artery.
Primary function is to Externally rotate hip during hip flexion.
Acts as Hip stabiliser during hip flexion and internal rotation.
- Gudena R, Alzahrani A, Railton P, Powell J, Ganz R. The anatomy and function of the obturator externus. Hip International. 2015 Sep;25(5):424-7.