Best answer: ask your doctor. Next best: arthritis is a disease of the joints, while MM (a disease of the bone marrow) generally damages, well, bones with marrow. Those are the long bones of the arms and legs and flat bones such as the pelvis and sternum. Gray zone: your back. Your spine is a series of joints, but the vertebrae do contain some marrow.

So pain in joints is likely arthritis, especially in older folks. Persistent pain mid-shaft in an arm or leg - in other words, not elbow, knee, ankle or wrist - in any MGUS, SMM, or MM patient should immediately be reported.