Purpose The purpose of this study was to gain an understanding of expert therapists' conception of physical therapy knowledge and to examine the application of therapeutic knowledge in clinical reasoning.Methods Open and semi-structured interviews were conducted with 13 expert physical therapists working in South Korea. The interviewed therapists had over 7 years of experience in physical therapy with over 5 years being devoted to one specialty. The interviews were thoroughly examined and reviewed, and then the data portions related to clinical reasoning were collected separately and analyzed qualitatively. Result Physical therapy knowledge was found to be generally applied across the entire treatment process from the interpretation and integration of given data, inferential identification and treatment of patients' problem to the consultation and education services to patients, the clinical interaction with colleagues, physicians, and other medical practitioners.Conclusion The results of the present study have implications for clinical practice, physical therapy education, and further research.