Diathermy uses an electric current to produce heat deep inside a targeted tissue. It can reach areas as deep as two inches from the skin’s surface. The diathermy machine does not apply heat directly to the body. Instead, the current from the machine allows the body to generate heat from within the targeted tissue. As the heat increases, it promotes blood flow. It also can help improve flexibility in stiff joints and connective tissues. With decreased pain and inflammation, patients with arthritis can increase their range of motion. This may allow them to move more easily and participate in rehabilitation more comfortably. Diathermy is a therapeutic treatment most commonly prescribed for joint conditions such as rheumatoid arthritis and osteoarthritis.