Reliability and validity of the Chinese version of the Short Musculoskeletal Function Assessment questionnaire in patients with skeletal muscle injury of the upper or lower extremities

BACKGROUND: The Short Musculoskeletal Function Assessment (SMFA) questionnaire is one of the most commonly used scales to evaluate functional status and quality of life (QOL) of patients with a broad range of musculoskeletal disorders. However, a Chinese version of the SMFA questionnaire for the psychometric properties of skeletal muscle injury patients in China is still lacking. The current study translated the SMFA into Chinese and assessed its reliability and validity among Chinese patients with skeletal muscle injury of the upper or lower extremities. METHODS: The original SMFA was translated from English into Chinese and culturally adapted according to cross-cultural adaptation guidelines. A multicenter cross-sectional study was conducted, comprising 339 skeletal muscle injury patients (aged 20–75 years) from 4 hospitals. The SMFA, the health survey short form (SF-36) along with a region-specific questionnaire (including the disabilities of the arm, shoulder, and hand questionnaire (DASH), the hip disability and osteoarthritis outcome score (HOOS), the knee injury and osteoarthritis outcome score (KOOS), and the foot function index (FFI)) were completed according to the region of injury. Reliability was estimated from the internal consistency using Cronbach’s α and validity was assessed via convergent validity, known-groups comparison, and construct validity. RESULTS: Cronbach’s α coefficient was over 0.75 for two subscales and four categories of the SMFA, suggesting that the internal consistency reliability of the SMFA was satisfactory. Known-groups comparison showed that the dysfunction index and the bother index of the SMFA discriminated well between patients who differed in age, gender, injury location, and operation status rather than in subgroups based on the body mass index (BMI). The convergent validity of the SMFA was good, as moderate to excellent correlations were found between the subscales of the SMFA and the four subscales of SF-36 (physical function, role-physical, bodily pain, and social functioning) and the region-specific questionnaires. The construct validity was proved by the presence of a six-factor structure that accounted for 66.85 % of the variance. CONCLUSION: The Chinese version of the SMFA questionnaire is a reliable and valid instrument to measure patient-reported impact of musculoskeletal injuries in the upper or lower extremities.