Sudden Debilitation, Not Arthritis?

Dear Sir /Ms; My family is looking for another opinion about my mother's condition. What do you suggest? My mother is in her late 70s. Six months ago she was perfectly fine. Now she can barely move. Her current Primary care Physician and Osteopathic Physician both feel she has Osteoarthritis. We also have family friends in the medical profession. One family friend just graduated from medical school this year, the other has one year to go before graduation. Our family friends who live out of State were visiting recently and kind enough to do a physical examine of my mom and check her X-ray which we had on CD. They said no Arthritis (Osteoarthritis or Rheumatoid Arthritis) in their opinion. They felt it was some kind of tendonitis. Both sides are saying different things and can't both be right. With all do respect to the doctors and their good intentions we (our family) feel that it is neither Arthritis or Tendonitis. The reason is my moms rapid movement deterioration. In October 2005 she had full and complete movement with no pain. Then all of a sudden in November 2005 both shoulders at the same time became extremely painful to the point that she could no longer even put on her coat by herself without difficulty. It was in November and December that we saw the doctors, had the blood test done and got the shot of cortisone in both shoulders. We were then told to make an appointment in March. The appointment was made. The examination is next week. Before we go however we would like to do a little research on our own to help our doctors. These days patients are encouraged to give a helping hand and be active participants in their health care. We don't want to go empty handed to the upcoming examination asking, what now? We prefer to go in and say this is what we have learned, what do you think?; Its all too easy for doctors to think outside of the box feeling: Patient in late 70s, no previous Arthritis, now Arthritis, is the to be expected box. Why the family feels this is neither Arthritis or Tendonitis is the rapid movement deterioration. In the couple months since her last examination my mother now can barely walk. Both legs are so painful now she can barely move them. Six months ago she moved faster than I move and I am a healthy 51 years old. Also within the last couple months she can barely move her neck or her fingers. She additionally seems to have lost a lot of strength and stays tired all the time. All of this has happened since her last examination (when only her shoulders bothered her), (the cortisone shots worked for two days) in December. If I'm not mistaken there are over 100 different types of Arthritis, and none of them progresses in this manner. What do you think my mother might have if its not Arthritis? How best do you think it should be treated? My mothers primary care doctor is in his 70s and has retired two or three previous times. We don't know how interested he is in maintaining his practice much longer. Her Osteopathic Physician specializes in sports medicine. Our family friends are young (in their 20s) and live out of State (additionally, one has another year to go before graduation). We therefore are open to switching doctors if we get a good recommendation of a doctor in our area who is accepting new patients. At my mothers rapid rate of movement deterioration we (the family) feel an urgent need to correctly diagnose and hopefully reverse this process before it goes further. Bottom line, we need any information and or leads that you think might help. Thank you very much.