STUDY DESIGN.: This was a cross-sectional study. OBJECTIVE.: We sought to test the psychometric properties of the modified lower extremity functional scale (LEFS) for low back pain (LBP). SUMMARY OF BACKGROUND DATA.: Low back and lower extremities are anatomically and functionally related, and radiating leg pain is common among patients with LBP. The LEFS is a reliable and valid questionnaire for patients with lower extremity conditions caused by musculoskeletal disorders, although its utility in LBP with or without radiating leg pain has not been tested. METHODS.: We recruited subjects with LBP from physical medicine and rehabilitation outpatient clinics whose age was at least 18 years. The evaluation included demographic data, back pain history, pain intensity by the visual analogue scale, the Roland-Morris Disability Questionnaire, and the modified LEFS, in which "lower limb problem" was substituted with "low back/lower limb problem" in the introductory sentence of the questionnaire. Data from 242 patients were analyzed for the psychometric properties of the modified LEFS, including floor and ceiling effects, internal consistency, test-retest reliability, dimensionality, and construct validity. RESULTS.: The modified LEFS had no floor or ceiling effects, high internal consistency (Cronbach α: 0.94), and good test-retest reliability (intraclass correlation coefficient[2,1]: 0.86). Principal component analysis identified one major factor that had an eigenvalue of 9.9 and explained 49.6% of the total variance. The correlations between the modified LEFS and Roland-Morris Disability Questionnaire was high (Pearson correlation coefficient: -0.71). The modified LEFS also discriminated well between the subgroups of LBP with unilateral leg pain and those with bilateral leg pain. CONCLUSION.: The modified LEFS had satisfactory psychometric properties in patients with LBP and could serve as a supplementary outcome measure to assess their activity limitations.
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