Sensitivity to change of mobility measures in musculoskeletal conditions on lower extremities in outpatient rehabilitation settings

Study design: Prospective longitudinal study. Objective: To examine the sensitivity of the Mobility Activities Measure for lower extremities and to compare it to the sensitivity of the Physical Functioning Scale (PF-10) and the Patient-Specific Functional Scale (PSFS) at week 4 and week 8 post-hospitalization in outpatient rehabilitation settings. Background: Mobility Activities Measure is a set of short mobility measures to track outpatient rehabilitation progress: its scales have shown good properties but its sensitivity to change has not been reported. Methods: Patients with musculoskeletal conditions were recruited at admission in three outpatient rehabilitation settings in Spain. Data were collected at admission, week 4 and week 8 from an initial sample of 236 patients (mean age +/- SD = 36.7 +/- 11.1). Main outcome measures: Mobility Activities Measure scales for lower extremity; PF-10; and PSFS. Results: All the Mobility Activities Measure scales were sensitive to both positive and negative changes (the Standardized Response Means (SRMs) ranged between 1.05 and 1.53 at week 4, and between 0.63 and 1.47 at week 8). The summary measure encompassing the three Mobility Activities Measure scales detected a higher proportion of participants who had improved beyond the minimal detectable change (MDC) than detected by the PSFS and the PF-10 both at week 4 (86.64% vs. 69.81% and 42.23%, respectively) and week 8 (71.14% vs. 55.65% and 60.81%, respectively). Conclusions: The three Mobility Activities Measure scales assessing the lower extremity can be used across outpatient rehabilitation settings to provide consistent and sensitive measures of changes in patients' mobility.