The answer is "yes" to exercise therapy for knee OA.  Three recent studies yield exercise-positive results.
D000328:Adult; D005081:Exercise Therapy / Q000379:methods*; D006801:Humans; D009788:Occupational Therapy / Q000379:methods; D015207:Osteoarthritis, Hip / Q000628:therapy; D020370:Osteoarthritis, Knee / Q000628:therapy*