Rusty, ydnar,
Inversion/eversion involves ankle joint and ankle musles as well as metatarsal forefoot area joints and muscles and is involved in passive rotation of femur.
The lateral rotation is originated in hip and actively rotates femur bone.
Here is the list of muscles which create lateral rotation (please note numerous muscles in hip area).
Gluteal Region:
-Piriformis
-superior gemellus
-obturator internus
-inferior gemellus
-obturator externus
-partially gluteus maximus
Anterior Compartment of Thigh
-partially sartorius
Medial Compartment of Thigh
-adductor longus
-adductor magnus
Posterior Compartment of Thigh
-biceps femoris
By contrast here are the muscles involved in inverting the foot. All these end somewhere in the foot mostly in the metatarsal area and FOOT IS WAY BELOW HIP.
I have omitted bunch of muscles which operate toes (but I think nobody will question how high in the kinetic chain they are).
FOOT INVERSION:
Anterior Compartment of the Leg
-tibialis anterior
-extensor hallucis longus
Posterior Compartment of the Leg
-tibialis posterior
Can you be more specific which of the muscles externally rotate your feet?
Robert