I have a four year old bloodhound. He weighs 145 pounds, but is not over-weight as he is very long and tall. The past two weeks when he first wakes up or gets up, he seems to favor his right leg to the point of not putting full weight on his paw. After he is up and moving for awhile, he seems fine. It does not hurt him if you rub or grab his leg or ankle area, but he will not let you touch his paw at any time, so I can not tell if it might be the paw. He does occasionally hold his paw off the ground.
Your pet should be seen by a vet for a diagnosis. He may need an x-ray. Good luck, vetcare