The Spanish Version of the Functional Rating Index in Patients With Low Back Pain: Preliminary Results of the Validation Study.

Objective: To assess the reliability, validity, and the psychometric properties of the Spanish version of the Functional Rating Index (Sp-FRI) in a preliminary cohort of patients with low back pain (LBP).

Design: Prospective observational multicenter study.

Setting: Outpatient physical therapy clinics and units from public and private settings.