Mutiple causes. Joint inflammation (arthritis) is one cause of painful and stiff joints, but not the only cause. Without other clinical information it would be difficult to give a more specific answer. If these symptoms have been present for more than 6 to 8 weeks you should probably be evaluated by your physician.
Rheumatoid arthritis. It could be rheumatoid arthritis. Get checked out by a rheumatologist. They will usually obtain some blood work, that may detect a problem.