My older dog has begun to have a hunchback / curved spine?

I have a 13 year old rat terrier, always been pretty healthy save for a couple of seizures every year which is common for his breed (we took him to the vet for this when he was younger). Recently I have noticed he has a hunch back or curved spine. He seems to not be in any pain and does everything he used to do just fine. I'm just wondering if this is just a sign of aging like in older humans or if it was trauma related? And either way is there anything I should be doing?