The Collaborative International Dictionary of English v.0.48:

osteopathy \os`te*op"a*thy\, n. [Osteo- + Gr. pa`qos suffering.]
   (Med.)
   (a) Any disease of the bones. [R.]
   (b) A system of treatment based on the theory that diseases
       are chiefly due to deranged mechanism of the bones,
       nerves, blood vessels, and other tissues, and can be
       remedied by manipulations of these parts. Modern
       practitioners use the therapeutic and diagnostic
       techniques of modern medicine as well as manipulative
       procedures.
       [Webster 1913 Suppl. +PJC]

WordNet (r) 3.0 (2006):

osteopathy
    n 1: therapy based on the assumption that restoring health is
         best accomplished by manipulating the skeleton and muscles