Diagnostic classification and orthopaedic physical therapy practice: what we can learn from medicine.

Concepts of diagnosis and classification have a long history in medicine, while formal schemes of diagnostic classification in physical therapy are relatively new. Basic differences exist between medicine and physical therapy in the phenomena which are diagnosed and classified. However, similarities in the diagnostic and classification process provide an opportunity to learn from medicine as the process now evolves in physical therapy. This paper provides a brief history of the development of the concept of diagnostic classification in medicine and physical therapy. Difficulties associated with the process are described. Knowledge of these difficulties is used to analyze some of the evolving concepts of diagnostic classification in physical therapy, especially those related to orthopaedic physical therapy practice.