The present study had the objective of evaluating the psychometric characteristics of the shortened 16-item version of the German Short Musculoskeletal Function Assessment questionnaire (XSMFA-D), which was designed for routine assessment of functional capacity in patients with various orthopaedic disorders treated either surgically or medically.
A total of 382 patients from seven different samples with either osteoarthritis of the knee, osteoarthritis of the hip, rheumatoid arthritis or rotator cuff tear treated either in surgical hospitals or rehabilitation settings were assessed both before and after treatment. The XSMFA-D was compared with both questionnaires measuring similar constructs and widely accepted indicators of health status in musculoskeletal disorders. Psychometric characteristics were computed.
The internal consistency (Cronbach's alpha) exceeded 0.90 in most cases for the function index and was between 0.80 and 0.90 in most cases for the bother index of the XSMFA-D. Retest-reliability was between 0.80 and 0.95 for the function index and between 0.60 and 0.92 for the bother index. Correlations between the XSMFA-D subscales and the other questionnaires were substantial, showing construct validity. Criterion validity was also demonstrated as significant relationships with accepted external parameters such as function tests, judgements by physicians, pain self-ratings by patients and disease severity scores were found. Sensitivity to change was as high as for the other assessment instruments used in this study.
The XSMFA-D, a very short assessment instrument, proved to be practical, reliable, valid and sensitive to change among the various patient samples studied. It may be recommended for the assessment of patients' state as well as the evaluation of treatments.