TENS machine treats many kinds of pain. The TENS nerve stimulator can help lessen acute (short-term) pain, like after surgery or an accident. Chronic pain (long-term), like arthritis, back or muscle pain, or cancer pain may also be lessened with tens electrotherapy device. Some people have trouble taking pain medicine. TENS is a safe, drug-free way to help control pain for these people as well. Patented pain-relief technology for treating sore muscles and joints and to relieve recent bruising and muscle pain where injury is relatively superficial such as sports related muscle strains.