Development and validation of an index of musculoskeletal functional limitations.
BACKGROUND
While musculoskeletal problems are leading sources of disability, there has been little research on measuring the number of functionally limiting musculoskeletal problems for use as predictor of outcome in studies of chronic disease. This paper reports on the development and preliminary validation of a self administered musculoskeletal functional limitations index.


METHODS
We developed a summary musculoskeletal functional limitations index based upon a six-item self administered questionnaire in which subjects indicate whether they are limited a lot, a little or not at all because of problems in six anatomic regions (knees, hips, ankles and feet, back, neck, upper extremities). Responses are summed into an index score. The index was completed by a sample of total knee replacement recipients from four US states. Our analyses examined convergent validity at the item and at the index level as well as discriminant validity and the independence of the index from other correlates of quality of life.


RESULTS
782 subjects completed all items of the musculoskeletal functional limitations index and were included in the analyses. The mean age of the sample was 75 years and 64% were female. The index demonstrated anticipated associations with self-reported quality of life, activities of daily living, WOMAC functional status score, use of walking support, frequency of usual exercise, frequency of falls and dependence upon another person for assistance with chores. The index was strongly and independently associated with self-reported overall health.


CONCLUSIONS
The self-reported musculoskeletal functional limitations index appears to be a valid measure of musculoskeletal functional limitations, in the aspects of validity assessed in this study. It is useful for outcome studies following TKR and shows promise as a covariate in studies of chronic disease outcomes.
Katz
Jeffrey N
JN
Department of Orthopaedic Surgery, Division of Rheumatology, Brigham and Womens' Hospital, Department of Epidemiology, Harvard School of Public Health, Boston, USA. jnkatz@partners.org
Wright
Elizabeth A
EA
Baron
John A
JA
Losina
Elena
E
D000203:Activities of Daily Living / Q000523:psychology; D000368:Aged; D000369:Aged, 80 and over; D040561:Assisted Living Facilities / Q000706:statistics & numerical data; D002908:Chronic Disease / Q000523:psychology / Q000534:rehabilitation; D004185:Disability Evaluation; D005260:Female; D006306:Health Surveys; D006801:Humans; D008297:Male; D051346:Mobility Limitation; D009140:Musculoskeletal Diseases / Q000175:diagnosis* / Q000503:physiopathology / Q000523:psychology; D017063:Outcome Assessment, Health Care / Q000379:methods; D011237:Predictive Value of Tests; D011788:Quality of Life / Q000523:psychology; D015203:Reproducibility of Results; D012647:Self-Assessment; D011795:Surveys and Questionnaires