Osteopathy was originally pseudoscientific quackery, but has long abandoned the woo crap that was not supported by medical evidence. Osteopathic medicine today is grounded firmly and exclusively in actual science.
Physical therapy is, and always has been, medical science based therapy.
Chiropractic therapy is founded upon disproven theories and requires no actual medical training. The industry regulates its own certifications, and chiropractors are taught a perverted concept of physiology.