At its simplest level electrotherapy can be defined as the treatment of patients by electrical means. By application this means that electrical forces are applied to the body bringing about physiological changes for therapeutic purposes. Physical agents like heat, light, sound, and mechanical modalities used in management of pain and regaining power and mobility.The modalities include various method of heating or cooling the tissues ultrasound, electromagnetic radiations, medium and low frequency currents, iontophoresis and phonophoresis.

Low frequency currents: This type of currents alternate at 1 – 1000 Hz. At this frequency currents can stimulates both motor and sensory nerves. Faradic type and galvanic type current used as low frequency current for therapeutic purposes.

Faradic Currents produce a tetnic contraction and that electrical muscle stimulation is usually achieved by 0.1 – 1 ms pulses at frequencies between 30 and 100 Hz. Faradism can be used to facilitate a muscle response and regain normal muscular strength and action. Reduction of oedema, prevention and loosening of joints adhesion by the application of faradic stimulation is common.

Ultrasound: This is the production of longitudinal mechanical waves above the audibla range(20kHz). The frequency used in physiotherapy vary from 0.75 MHz to 3 MHz.These are produced by distortion of a quartz crystal by a high frequency alternating current. Physiological effects of ultrasound accelerate the healing process and results in pain relief. Ultrasound may be used in resent soft tissue injuries, back pain, recent and chronic scar tissues, skin grafts and venous ulcer or pressure sore.