What is the difference between osteoporosis and osteoarthritis?

Very different: Osteoporosis refers to thinning of the bones and generally affects the whole skeleton. It is a painless process unless a fracture occurs. Osteoarthritis refers to a painful joint disease due to narrowing of the joints so bone may be rubbing on bone. It may commonly affect the joints of the hips, knees, or hands.

Pain: Osteoporosis is a painless decrease in the minerals within bone causing it to lose density where arthritis is inflammation of a joint from any number of sources.