Whats the difference between degenerative disk disease and osteoarthritis?

I had cervical fusion 10 years ago. I have been told the I have degenerative disk disease, degenerative spine disease and now osteoarthritis. I was told at the er that x-rays showed bone spurs in my lumbar spine and now in my thoracic spine. Needless to say my legs and arms hurt all the time. I have began to start dropping alot of stuff that I am holding in my left hand and my right legs continues to cause me to fall. Does anyone know if there is a difference in these diagnosis or is it all the same thing? Thanks to anyone who has an answer.