The iliopsoas muscle and the lumbar spine.

The influence of the iliopsoas muscle length on postural and mobility characteristics of the lumbar spine was investigated in 60 normal male subjects. The passive physiological and accessory intervertebral movements were assessed. Measurements which provided estimations of the lumbar lordosis, lumbar extension and iliopsoas muscle length were also recorded. A difference was found in the iliopsoas muscle length with respect to the mobility of the passive physiological and accessory intervertebral movements at the L1-L2 and T12-L1 segments, and at the L2 and L1 levels respectively. As the iliopsoas muscle shortened, the intervertebral mobility increased. Furthermore, the iliopsoas muscle length showed a weak tendency toward a correlation with the lordosis and the lordosis tended to increase as the muscle shortened. No correlation was found between the iliopsoas muscle length and the range of lumbar extension.