The amount of rotation at the lumbosacral joint was studied in nine healthy young men by placement of pins into the spinous process of the fifth lumbar vertebra and into the posterior superior iliac spines of the pelvis. In this sample, approximately 6.0 degrees of rotation were found to occur at the lumbosacral joint during maximum rotation when the subject was either standing or straddling a bicycle seat with his pelvis fixed. Approximately 1.5 degrees of rotation occurred during normal walking. Rotation at the lumbosacral joint was not measurably affected by asymmetrically oriented lumbosacral facets. It was always associated with flexion of the fifth lumbar vertebra on the sacrum.

Immobilization of the lumbosacral joint by the use of a modified chairback brace was relatively effective in restricting rotation. The effects of a lumbosacral corset on immobilization were varied and unpredictable. Adequate fixation of the pelvis is essential to achieve restriction of motion; inadequate fixation may allow proximal rotatory motion to be transmitted to more distal levels. External immobilization with the corset or brace used in this study does not appear to decrease lumbosacral rotation during normal level walkinig; in our subjects, it caused an increase.