Analysis of the Convergent and Discriminant Validity of Published Lumbar Flexion, Extension, and Lateral Flexion Scores

STUDY DESIGN: Articles reflecting the convergent or discriminant validity of the lumbar range of motion tests were reviewed and compared. Mean scores and standard deviations for lumber range of motion from healthy control subjects were plotted against those from patients with low back injuries. OBJECTIVE: To use published research to analyze the convergent and discriminant validity of lumbar range of motion tests for the characterization of low back pain and injury. SUMMARY OF BACKGROUND DATA: Several publications have addressed lumbar range of motion validity. Individual studies suggest that the tests possess convergent validity, but that their discriminant validity is indeterminate. METHODS: English-language journals were searched on Medline using "region," "lumbar," "range of motion," "validity of results," "observer variation," and "low back pain" as title and subject search terms. The study methods approximating the specifications of the American Medical Association Guides to the Evaluation of Permanent Impairment were included in the analysis. RESULTS: Convergent validity research showed inconsistent relations between inclinometric and radiographic lumbar range of motion measurements. Some studies showed strong relation, whereas others showed essentially no relation between the two techniques. Correlations between lumbar range of motion scores and spinal disability and function were similarly inconclusive. Studies reporting mean scores and standard deviations for lumbar range of motion measurements showed a high degree of overlap between the scores of participants with low back injuries and those without such injuries. CONCLUSIONS: Convergent and discriminant validities of the lumbar range of motion tests currently require further substantiation. Absolute lumbar range of motion scores may not be suitable as the sole determinants of low back pathology diagnosis. Implications for using the lumbar range of motion tests to characterize low back injuries in medicolegal situations are discussed.