The Spanish lower extremity functional scale: a reliable, valid and responsive questionnaire to assess musculoskeletal disorders in the lower extremity.

PURPOSE: The Lower Extremity Functional Scale (LEFS) is a widely used questionnaire to evaluate the functional impairment of a patient with a disorder of one or both lower extremities. It also can be used to monitor the patient over time and to evaluate the effectiveness of an intervention. Nevertheless there is no Spanish version of the LEFS, so the aim of this study was the translation and cross-cultural adaption of the Spanish version of the LEFS and to evaluate its psychometrics properties.

METHODS: The questionnaire was cross cultural adapted into Spanish. The psychometric properties tested in the Spanish version of the LEFS were: internal consistency, test-retest reliability, constructs validity, discriminative validity, responsiveness, concurrent validity and floor and ceiling effects in 132 participants seeking for treatment due to lower extremity dysfunction.

RESULTS: The Spanish version of the LEFS had high internal consistency (Cronbach's α=0.989), test-retest reliability (ICC=0.998, 95% CI: 0.996-0.999) and presented a high correlation with the SF-36 (36-Item Short-Form Health Survey) especially with the physical function and pain subscales. The construct validity showed a single factor that account for 84.95% of the variance. The standard error of measurement of the Spanish version of the LEFS was 0.88 scale points (95% CI) and the minimal detectable change was 2.18 scale points (95% CI). The sample, collected from five Spanish physical therapy centers, was divided in groups (acute, sub-acute and chronic subjects). Within group changes showed a significant improvement on the LEFS score (p<0.001) and effect sizes were large in all conditions. The LEFS allowed to distingue between acute and not acute conditions; for this criterion ROC curve was performed at baseline (area under the curve [AUC]=0.95). There was no floor or ceiling effects.

CONCLUSIONS: The Spanish version of the LEFS has been shown to be a valid and reliable tool to assess musculoskeletal dysfunction in the lower extremity that could be used with Spanish speaker population. Implications for Rehabilitation Cross-cultural adaptation of a self-reported questionnaire to evaluate musculoskeletal lower extremity disorders in the Spanish population. To provide Spanish clinicians and physiotherapists a useful tool to assess the lower extremity function. To provide Spanish researchers a valid tool for research on lower extremity function: patient's improvement due to treatment, compare results obtained between populations, treatment.