A "thing leg" is not a standard term, but it could refer to a structural component or support leg in various contexts, such as furniture or machinery. If you meant a specific item or concept, please provide more context for a clearer answer.
There is no such thing as a doctor that specializes in leg injuries. If you have a leg injury, you should go to your local emergency department for treatment.
In England we call it 'cocking' their leg.
A tortoise leg
Hind leg, flank, back leg, or rear leg.
Lotion
The fingers on the leg are known as toes.
you call it a leg that has been hurt not severely but maybe damaged somehow
pleopod
Quadraped.
Handicapped.
a limb
lame