On the other side there are also times when she does appear to be happy and energetic, almost like her real self. In a couple of pretty large studies of dogs there was a high incidence of visible spondylosis deformans on X-rays and no correlation at all with lameness or pain. It is very hard to determine if pets are in pain since they are often pretty good at hiding it or are just willing to accept it and function anyway. For this reason, if a problem is usually painful in humans it is best to assume that it is painful in pets and just treat accordingly. I can attest to the pain associated with disc herniation and am very quick to treat patients with pain medications due to this personal experience.
Prednisone is a corticosteroid.
These hormones are regulated by the brain, which stimulates production when levels are too low and inhibits it when levels are too high. The dosage of corticosteroids used as anti-inflammatory medications is high enough to turn off the body's own production of corticosteroids. If this situation goes on long enough, the body won't be able to respond to a need for cortisones when one arises. Early in the use of cortisone this need was not recognized and some patients died when corticosteroids were withdrawn abruptly. The risk of this is minimized by using the medications on an every other day basis.