Because Ive had chickens with sour crop so bad that they cant walk.Its a symtom of that disease.Ive lost birds misdiagnosed due to ill-advisement on sour crop (not on this site),and they said they got them fron a chicken trader so who knows how they had their chooks.
But thank you for saying I dont have good advice.
is your roos legs broken?
is he missing legs,toes or the like?
does he have something stuck or stabbed in his legs?
is his legs entangled with netting,rope,wire,or the like that he cannot stand?
does he have bugs attached and draining his leg power?
does he have a chunk of kryptonite tied on him somewhere?
if
NOT, then check its crop. Sour crop will make them be lethargic,then their wings will droop,then their abdomen and crop will be squshy,then they will sit and wont stand,then in a day or so die.
Pickaduck, how can you say my advice isnt good,since I got it from peeps here?