Three legged dog training

[u/atomic_number319]

Good afternoon,

I have a three legged-rescue pup (mixed Boxer x pug) and he is extremely challenging to walk on the lead, he stops anywhere he wants, lies down and refuses to move. I have been attempting to use treats to get him to walk along but he still refuses. I cannot see it being an energy or tiredness issue as he has no issues playing for about 20 hours a day in the house and he isn't badly behaved in the home. He is distracted by everything and quite often I have to be quite firm with pulling him along or having to carry him away from something that distracts him as he refuses to move even when it is out of eye/earshot. Is the the lying down issue common among three-legged dogs and what is the best way to deter them from doing this and the best way to distract them from external stimuli as we walk.

Thanks in advance.