My Dog Wont Wag or Lift his Tail

Question
I have a 6 year old lab/retriever mix. He got out of the yard the other night and was gone until the next morning. He was laying out front and when i saw him i called to him and he wouldnt move. Then when he did come to me his tail looked limp and he wasnt wagging it. I wasnt yelling or mad at him, he is a very happy boy. Now its been another day and he is acting sad and wont lift his tail or wag it. I am thinking somebody injured him when he was out the other night.? He doesnt seem to be in pain but he seems uncomfortable. He is eating but not very much. He just isnt himself. If somebody did something to him what could they have done? What could have happend? I am worried and disturbed by it. What should i do? I dont want to rush him to the vet. if not neccessary, money is tight...But of course i will if need possible. What do you think could have happend? What should i do?
Thank you for your time.
Meghan

Answer
Most of the time when this happens the dog has been struck by something (like bumped by a car) or has injured his lower back. The muscles that wag the tail are around the sacrum (where the hips join the spine) so if the sacrum is injured, the dog won't want to move or wag his tail.

You can check his toenails to see if a car bumped him because they will be worn down and splintered looking- or you can see if he has road rash on the inside of his legs.

They can hurt their sacrum or lower back by running up hills, jumping off of furniture or other things, and from twisting while running after a cat or something.

If he were my dog I would have the vet look him over. You can make sure his tail isn't broken that way and get some safe anti-inflammitories for him.