Chiropractic is a health care profession that focuses on disorders of the musculoskeletal system and the nervous system, and the effects of these disorders on general health. Chiropractic care is used most often to treat neuro- musculoskeletal complaints, including but not limited to, back pain, neck pain, pain in the joints of the arms or legs, and headaches. Doctors of Chiropractic, often referred to as chiropractors or chiropractic physicians, practice a drug-free, hands-on approach to health care that includes patient examination, diagnosis and treatment. Chiropractors have broad diagnostic skills and are also trained to recommend therapeutic and rehabilitative exercises. The most common therapeutic procedure performed by chiropractors is known as "spinal manipulation," also called "chiropractic adjustment." The purpose of manipulation is to restore joint mobility by manually applying a controlled force into joints that have become restricted in their movement as a result of a tissue injury. Tissue injury can be caused by a single traumatic event, such as improper lifting of a heavy object; or through repetitive stresses, such as sitting in an awkward position with poor spinal posture for an extended period of time. In either case, injured tissues undergo physical and chemical changes that can cause inflammation, pain, and diminished function for the sufferer. Manipulation or adjustment of the affected joint and tissues restores mobility, thereby alleviating pain and muscle tightness, and allowing tissues to heal.