Osteopathy, practice of therapy based on manipulation of bones and muscles. This system of medicine, founded by A. T. Still in 1874, maintains that the normal body produces forces necessary to fight disease and that most ailments are due to "structural derangement" of the body. Frequent slight strains are held to be capable of causing misalignment of bones and various other conditions of the muscle tissue and cartilage, and treatment is directed toward correction of these conditions.