Possibly because it has injured it's hind leg(s) and it hurts to walk on them. Try having your dog lay in your lap and take a look at the hind legs, if they're isn't anything visible wait and see if it goes away ( It could have been a cramp) and if it doesn't, call the vet.
Then your dog has more than one broken leg and it might be a birth defect. Your dog doesn't need to be able to stand on its hind legs to be healthy.
Donald, of course! Stay with the Disney theme. BUT don't tell him he has no hind legs! ^ WRONG you call him Billy
just like alot of dogs have long hind legs but they longest dog legs ive seen were from a great dane
The legs may shake if the dog is frightened.
hind-quarters
Yes, a dog who has hip dysplasia can climb stairs if a hind leg is lame.
Yes. Their knees are located on the hind legs where the patellas* are. You can tell where they are when a dog's hind legs bend before the hocks*. *knee caps *ankles You can use this link to have a full view of a dog's skeleton: http://www.pets.ca/pics/dogskelsys.gif
leash may be too tight causing strain on hind legs or may be perfectly natural for dog. try loosening leash. if dog is jack russell then may well be pulling on hind legs
A female dog has one vagina. It is between her hind legs and below the anus.
5 feet 6 inches
It means its a human dumbo. idiot
heart worms if not treated can kill it