What specialist is for osteoarthritis?

Orthopedics. Particularly if it is bad enough to require joint replacement therapy- for this you would see an orthopedic specialist. If it's not that bad, you can be treated by your internist or family practitioner.
Several. The specialists that typically deal with arthritis are rheumatologists, physiatrists and orthopedists. They all have different training after medical school but their goals are them same to minimize the pain and improve function in people with arthritis. '.