Lumbar disc degeneration and sagittal flexibility.

It is uncertain whether intervertebral disc degeneration is associated with reduced or increased flexibility, although lumbar flexibility is known to reduce with advancing age. This cross-sectional study of 214 middle-aged men attempted to determine the influence on lumbar sagittal flexibility from intervertebral disc degeneration parameters measured from magnetic resonance images (disc height, signal intensity, bulging, osteophytes). Multivariate analyses showed that a reduced extent of lumbar flexibility could be accounted for by the combined effect of decreasing disc height together with increasing age, weight, and back pain frequency. Although it remains possible that single degenerate discs will display increased mobility, the presence of discs at various stages of degeneration results in a net reduction of flexibility. The factors studied here explained only 31% of the variance in flexibility; the major determinants remain to be identified and quantified.