<P> Chiropractic is a form of alternative medicine mostly concerned with the diagnosis and treatment of mechanical disorders of the musculoskeletal system, especially the spine . Proponents claim that such disorders affect general health via the nervous system, through vertebral subluxation, claims which are demonstrably false . The main chiropractic treatment technique involves manual therapy, especially spinal manipulation therapy (SMT), manipulations of other joints and soft tissues . Its foundation is at odds with mainstream medicine, and chiropractic is sustained by pseudoscientific ideas such as subluxation and "innate intelligence" that reject science . </P> <P> Numerous controlled clinical studies of treatments used by chiropractors have been conducted, with conflicting results . Systematic reviews of this research have not found evidence that chiropractic manipulation is effective, with the possible exception of treatment for back pain . A critical evaluation found that collectively, spinal manipulation was ineffective at treating any condition . Spinal manipulation may be cost - effective for sub-acute or chronic low back pain but the results for acute low back pain were insufficient . The efficacy and cost - effectiveness of maintenance chiropractic care are unknown . There is not sufficient data to establish the safety of chiropractic manipulations . It is frequently associated with mild to moderate adverse effects, with serious or fatal complications in rare cases . There is controversy regarding the degree of risk of vertebral artery dissection, which can lead to stroke and death, from cervical manipulation . Several deaths have been associated with this technique and it has been suggested that the relationship is causative, a claim which is disputed by many chiropractors . </P> <P> Chiropractic is well established in the United States, Canada, and Australia . It overlaps with other manual - therapy professions such as osteopathy and physical therapy . Most who seek chiropractic care do so for low back pain . Back and neck pain are considered the specialties of chiropractic, but many chiropractors treat ailments other than musculoskeletal issues . Many chiropractors describe themselves as primary care providers, but the chiropractic clinical training does not support the requirements to be considered primary care providers, so their role on primary care is limited and disputed . Chiropractic has two main groups: "straights", now the minority, emphasize vitalism, "innate intelligence", and consider vertebral subluxations to be the cause of all disease; "mixers", the majority, are more open to mainstream views and conventional medical techniques, such as exercise, massage, and ice therapy . </P> <P> D.D. Palmer founded chiropractic in the 1890s, after saying he received it from "the other world", and his son B.J. Palmer helped to expand it in the early 20th century . Throughout its history, chiropractic has been controversial . Despite the overwhelming evidence that vaccination is an effective public health intervention, among chiropractors there are significant disagreements over the subject, which has led to negative impacts on both public vaccination and mainstream acceptance of chiropractic . The American Medical Association called chiropractic an "unscientific cult" in 1966 and boycotted it until losing an antitrust case in 1987 . Chiropractic has had a strong political base and sustained demand for services; in recent decades, it has gained more legitimacy and greater acceptance among conventional physicians and health plans in the United States . </P>

What are the two main types of chiropractors