This is a modality in Acupuncture consisting of plastic or glass cups that creates a suction/pressure on the affected body area. During pain and inflammation muscles and tendons tend to block a free flow of blood, creating blood stagnation. 

This stagnation aggravates the medical condition (more pain) due to lack of or poor blood circulation. These suction cups bring more blood (to the affected area) consequently more oxygen, more nourishment-essential nutrients plus alert the immune system (White blood cells) about pain and inflammation. 

The Immune system will start a natural process of healing. Cupping will restore blood circulation to the affected area as result alleviating/ reducing pain and inflammation.