Chronic arthritic pain is just one part of the larger pain picture. Most pain is triggered by an injury such as a simple cut.

In the immediate seconds following injury, the body activates at a cellular level. Tiny blood vessels in the vicinity of the cut immediately contract. Specialized blood cells called thrombocytes and platelets become "sticky" and attach to collagen exposed by the cut. The platelets stick to one another and form the beginnings of a clot. They also release a stabilizing substance, fibrin, to bind the clot's matrix together.

Later, other cells called fibroblasts will migrate to the site and repair the cut to make the blood vessels and surrounding tissue whole once more. Meanwhile, the body has responded in another way—an alert has been sent out on a molecular level that an injury has occurred. The alert comes in the form of inflammation mediated by prostaglandins and bradykinin, natural substances produced by the body that are released by the damaged tissue. The presence of the prostaglandins and bradykinin produces further cellular changes. Nearby nerve cells are primed to transmit information from the site of injury to the brain. The brain responds to the molecular message with pain.

Other cells called leukocytes are attracted to the site of injury. Leukocytes, attempting to "clean up" damaged tissue at the injury site, prompt the rupture and leakage of enzymes from damaged cells. The enzymes released by this process go on to damage nearby, healthy tissue. The healthy tissue now becomes a part of the injury, and inflammation and pain spread. During an acute injury this scenario is played out until the cut or scrape stabilizes and begins to heal.