My lower back has been complaining loudly since I had the TKR. I have chronic problems with it, but using a walker and a cane really exacerbated the usual problems. Once I was able to ditch both (though I still use cane outdoors and if I'm tired) it began to improve. Having an altered gait also affects the back and it will take time to improve because we're using muscles that haven't been used or used correctly in a long time. I think the other aches and pains (shoulders, arms, wrists, hands) are also due to using walking aids and should subside once those are no longer needed. I use heat and massage on my back, along with some hamstring stretches and stretches for the piriformis muscle. YouTube has a lot of videos that demonstrate some great back stretches.
Are you certain you cannot lie on your stomach? I ask because an appointment with a deep-tissue, massage therapist would be very helpful. I've been once, about 2 weeks ago and it made a big difference.