Carol
Hi! I was sorry to hear of the pain your dad is in with osteo and rheumatoid arthritis. I also have symptoms, and found that SOMETIMES oranges and other citrus fruits irritate the disease, and sometimes not. I am using a SHAKLEE product called (here in Canada) Osteokinetics. It seems to help rebuild the cartilege, as I don't have as much pain or difficulty in using my arms. Perhaps your dad should substitute another fruit, such as apples, in his diet. He can get his Vitamin C in other ways, in vitamins, or in fruits such as strawberries and watermelon. Hope this helps a bit!