Original Research Dimensionality of Measures for Severe Unilateral Ankle Arthritis Chad Cook, PT, PhD, Robin M. Queen, PhD, Emily J. Slaven, PT, PhD, James K. DeOrio, MD, Mark E. Easley, MD, James A. Nunley, MD Objective: To analyze the dimensionality of 2 self-report outcome measures (Foot/Ankle Disability Index [FADI] and Short-Form [SF]-36), 3 biomechanical measures (stance and step symmetry measures, gait speed, and step width), 2 physical-performance measures (timed get-up and go [TUG] and 4-square step test [4SST]), and 1 clinician-report outcome measure (American Orthopaedic Foot and Ankle Society [AOFAS] Hindfoot Scale) in a patient population with unilateral ankle arthritis. These measures captured the following functions: mobility and speed, pain and its relationship to function, social integration, and symmetry and efficiency of gait. Design: Case series design. Setting: Biomechanical research laboratory adjacent to a busy orthopedic clinical practice. Patients: Seventy-nine consecutive patients with unilateral traumatic arthritis who were candidates for a total ankle replacement. Methods: An exploratory factor analysis with oblimin rotation was performed to deter- mine the dimensions of the physical performance, biomechanical, self-report, and clinician- report measures. Main Outcome Measurements: Outcomes measures included the SF-36 and perti- nent subscales, gait speed, the 4SST, the TUG, the FADI, the AOFAS Hindfoot Scale, and biomechanical measures of step width, step symmetry, and stance symmetry. Results: Four distinct dimensions were captured during factor analysis. Factor 1 included the TUG, gait speed, the 4SST, and step width; factor 2 included the FADI, the SF-36 bodily pain score, and the SF-36 physical function score; factor 3 included the biomechanical scores of stance symmetry ratio and the step symmetry ratio; and factor 4 included SF-36 social functioning and the AOFAS Hindfoot Scale. Conclusions: Findings suggest that various outcome measures for the ankle capture different dimensions and should be considered when evaluating the presence of disability or long-term change in outcome. PM R 2010;2:987-994 INTRODUCTION Ankle arthritis is a debilitating diagnosis that can lead to severe pain, deformity, and functional disability [1]. Arthritis may occur after trauma [2,3], including talus fracture [4], distal tibia fracture [2], tibiotalar joint injury [3,4], or a combination of these factors [4]. The arthritis and resultant deformity may lead to recurrent pain [1], biomechanical changes, cartilage breakdown, and subsequent gait dysfunction [1,5]. Although gait changes and pain are the most notable outcomes in patients with unilateral ankle arthritis, other measures, such as quality of life and function, also have been investigated and have reflected the significant levels of severity of this condition [5]. The degree of disability associated with ankle osteoarthritis is equivalent to that reported in populations of patients with medical problems such as end-stage kidney disease, congestive heart failure [6], and end-stage hip arthritis [7]. The exact nature of the disability is complex, and to date it has not been explicitly delineated. The International Classification of Functioning (ICF) defines functioning and disability as multidimensional concepts that involve (1) body function and structures, (2) activities C.C. Division of Physical Therapy, Walsh University, North Canton, OH 44720.Address correspondence to C.C.; e-mail: ccook@ walsh.edu Disclosure: nothing to disclose R.M.Q. Department of Orthopaedic Surgery, Duke University and Michael W. Krzyzewski Human Performance Lab, Duke University Medical Center, Durham, NC Disclosure: nothing to disclose E.J.S. Department of Physical Therapy and Occupational Therapy, Duke University Medi- cal Center, Durham, NC Disclosure: nothing to disclose J.K.D. Department of Orthopaedic Surgery, Duke University, Durham, NC Disclosure: 2B, Wright Medical and Integra; 3B, Tornier M.E.E. Department of Orthopaedic Surgery, Duke University, Durham, NC Disclosure: nothing to disclose J.A.N. Department of Orthopaedic Surgery, Duke University, Durham, NC Disclosure: nothing to disclose Disclosure Key can be found on the Table of Contents and at www.pmrjournal.org Submitted for publication February 10, 2010; accepted August 2, 2010. PM&R © 2010 by the American Academy of Physical Medicine and Rehabilitation 1934-1482/10/$36.00 Vol. 2, 987-994, November 2010 Printed in U.S.A. DOI: 10.1016/j.pmrj.2010.08.001 987