Hardly sounds a little like Rourke, he was nodding on his front leg and the problem turns out to be his shoulder, he also has a bony growth on the rear hind leg which is arthritis. He has arthritis in both shoulders, both front wrists and both rear hocks. His shoulder is the major problem, he has tendonitis and possibly a mechanical problem. Unfortunately he cannot take anti-inflammatories. The specialist orthopaedic vet was quite optimistic about controlling arthritis if the dog can take anti-inflammatories, so there is a lot of hope for Harley. I do hope the other lumps prove to be nothing, a worry for you until you know.