Iliolumbar Ligament Injury
Ross Hauser, M.D. Marion Hauser, M.S.,R.D.

The iliolumbar ligaments are very important and very strong ligaments connecting the lower lumbar vertebrae to the crest of the iliac bone. They run, posteriorly and laterally, from the transverse processes of the fourth and fifth lumbar vertebrae to the ilium.

The iliolumbar ligaments contribute, with the interspinous and supraspinous ligaments, to stabilize the lower lumbar spine on the base of the sacrum. The iliolumbar ligaments counterbalance the shearing forces of the fifth lumbar vertebra on the base of the sacrum and prevent the forward shifting of this vertebra as well as that of the fourth lumbar vertebra onto the fifth vertebra. If the vertebrae shift, the condition is called spondylolisthesis.  (See Figure 17-6.)

The iliolumbar ligaments, with the interspinous and supraspinous ligaments, by preventing the forward shifting of the fifth lumbar vertebra on the base of the sacrum, also prevent too much stress from being exerted on the disc and allow normal function of the facet joints. They also prevent the sacral base from excessively tilting forward and downward, thus helping keep a normal lumbosacral angle of approximately 40 degrees. With a normal lumbosacral angle, the curve of the spine (lordosis) is normal.

Trauma to the iliolumbar ligaments causes them to be weakened and also contributes to the degenerative process involved in most chronic low back pain sufferers. Injury to this ligament increases the likelihood of the fifth lumbar vertebra moving on the sacrum and the fourth lumbar vertebra slipping. This results in tearing of the outer layer of the disc and formation of fissures in the annulus. This is the mechanism of eventual disc herniation.

When the fifth lumbar vertebra shifts forward on the sacral base, a narrowing of the intervertebral foramen may form, resulting in compression of the nerve root (sciatic nerve). The person may then experience shooting pain down the leg. Laxity in the iliolumbar ligaments causes the sacral base to dip forward, resulting in an increase in the lumbosacral angle. When the lumbosacral angle is increased, lumbar lordosis increases. (Caillet, R. Low Back Pain Syndrome. Second Edition. Philadelphia, PA: F.A. Davis, 1972, p. 10-14.) This makes the athlete more prone to low back pain. The athlete may also notice the feeling of weakness in the back. If the problem is not stopped here with Prolotherapy, sacroiliac problems will soon follow.