Could be a broken bone or dislocation of joint get a xray from a vet will be helpful if u can if u cannot get Himalayas tablet Called ShigruHe can’t stand on his own he stands when I hold him like this. And when he sits sometimes he’s holding his leg like that. The straight leg is the injured one here.
Half tablet for 7 days it's a natural anti-inflammatory and help in knee issues
And.all.big combs stay purple due to poor circulation and get back normal once blood reaching that area
Also feed him good diet
Like boiled eggs , spinach , boiled vegetables
(No.rice until he's leg heal rice can create pus and inflammation)