| Knee osteoarthritis (KOA), one of the most prevalent disabling conditions in the United States, presents a significant public health challenge. Therefore, limiting the onset and severity of disability in KOA requires a thorough understanding of the trajectory of disability. Achieving this understanding is difficult, however, because of the lack of an organizing framework from which to examine disability and because of the number of factors associated with disability in KOA.; Using the International Classification of Functioning, Disability and Health (ICF) as an organizing framework, activity and activity limitations in KOA were studied to enhance the understanding of disability in KOA. Specific goals were (a) examining the state of the art of measurement of activity limitations in KOA, (b) ascertaining perceived activity limitations caused by KOA, and (c) determining if two commonly used self-report instruments measured activity similarly. Systematic literature reviews, qualitative research techniques, and Rasch Item Response Theory analysis were used to accomplish these goals.; The systematic review and qualitative research study indicated that overall, fewer activities were measured in research than described in the ICF, and activities not measured on commonly used instruments, described in the ICF, or reported in research, were identified as limitations by a group of persons with KOA. Rasch analysis demonstrated that both the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and Short Form-36 (SF-36) are needed to characterize function and disability in KOA. Furthermore, the Rasch Item Response Theory study indicated that relative activity difficulty could be used to develop an activity difficulty hierarchy.; Measurement of activity limitations in KOA requires further study to adequately describe activity and activity limitations in KOA. The ICF holds promise as an appropriate organizing framework for this purpose and both qualitative research techniques and Rasch analysis provided valuable information about activity limitation in KOA. |
