Physically, the smaller dogs are more prone to injury. I would be extra careful to try to limit his jumping on and off furniture or going up and down stairs.
We have a male that is 2.5 pounds and decided one day he was in too much of a hurry to go down ALL the stairs (all 5 of them). He skipped the last on, jumping from the 2nd, managed to land wrong, knocked himself out and injurred his knee.
