Gate Control Theory: According to this theory all pain impulse are controlled, modulated and modified by a functional gate, located in substantia gelatinosa of the spinal cord. Under normal circumstances, this gate is open allowing impulse an easy passage. The pain impulse comes to the spinal cord via posterior nerve root. Beyond this gate, the pain impulse crosses the other side of the spinal cord following the path up the spinothalamic tract to the thalamus and to the cerebral cortex. This is how the patient feels the pain. The whole process is almost instantaneous as the pain impulse travels at the rate of one meter per second.

After insertion of the acupuncture needle, a secondary stream of sensory impulses is generated. This impulse are non painful in character and travel along the large diameter fibers at much faster speed of about 120 meters per second. The two stream of impulse appear simultaneously at the functional gate giving rise to confusion and crowding hence pain is not felt. The immediate reaction is closure of gate causing an elevation in pain threshold so no pain is felt.

Endorphin Release Theory: Analgesic effect of acupuncture is due to the release of hormone called endorphin after needling. Endorphin is a naturally acting neuropeptide and like morphine has a tendency of binding on to the opiate receptors of pain cells.

Traditional Chinese Theory: Ancient Chinese had no knowledge of the nervous system, nor did they know of endorphin or prostaglandin. According to them mechanism of acupuncture depended upon five element , organ clock and pulse diagnosis. They believed as long as flow of energy is free and yin and yang are balanced, the person is healthy, obstruction to the flow of energy results in disease, and by inserting a needle at a particular predetermined points correct all irregularities. They used to take pulse of a patient from which they could judge the energy imbalance which they use to correct with the help of organ clock, five elements theory.