"Tend to" is the phrase.This front paws down, rear end up, posture is a play posture.Other dogs take it as an invitation to play and will adopt it to invite another to play. A dog with a bone will adopt it particularly when thinking of playing with the bone, tossing the bone in the air and grabbing it again for further chewing. I'd take chewing in this posture as a sign of a happy,contented, playful, dog but it's true that some individuals do opt to chew in this way, without then and there making play with the object..
Glad to hear of your dog's treatment and recovery!