Some medical doctors maintain that misaligned vertebrae-the chiropractor's clue to health problems-are common, often harmless, and do not require treatment. 

Critics charge that frequent visits to a chiropractor are useless, whether as a preventive measure or to treat a specific condition such as back pain-which, they say, usually clears up on its own. 

Those critical of chiropractic often point out that quadriplegics can have healthy internal organs despite their extensive nerve damage. This fact, they maintain, disproves the assertion that a sound nervous system is the key to overall health. 

A number of critics argue that chiropractors should restrict their practice to treating back pain, since there is insufficient evidence to show that manipulation provides relief from any other condition.