Which of the following is most commonly used in the treatment of arthritis?

The use of diathermy in the treatment of arthritis is effective because it involves the application of heat to promote blood flow, reduce stiffness, and alleviate pain in the affected joints. Diathermy utilizes electromagnetic currents to generate heat deep within body tissues, which can help to relax muscles and improve the range of motion. In many cases, this therapeutic approach is particularly beneficial for patients suffering from conditions like osteoarthritis and rheumatoid arthritis, as it can provide both symptomatic relief and improve function.

In contrast, radium, though historically utilized in some types of arthritis treatment, is less common now due to concerns about radiation exposure and the development of safer and more effective therapies. An electrocardiogram is a diagnostic tool used to assess heart function and is not related to arthritis treatment. A radiograph, or X-ray, is useful for diagnosing and monitoring arthritis but does not play a therapeutic role in its treatment.