What is the definition of medical necessity?

Health care services or products that a prudent physician would provide to a patient for the purpose of preventing, diagnosing, treating or rehabilitating an illness, injury, disease or its associated symptoms, impairments or functional limitations in a manner that is: (1) in accordance with generally accepted standards of medical practice; (2) clinically appropriate in terms of type, frequency, extent, site and duration; and (3) not primarily for the convenience of the patient, physician, or other health care provider.