Objective
This research aimed to define the relationship between the lower lumbar disc herniation and the morphology of the iliolumbar ligaments using magnetic resonance imaging.

Method
24 male and 36 female patients were classified into two groups according to their disc herniation grade- those in whom the L5-S1 disc was less herniated than L4-5 disc, those in whom the L5-S1 disc was more herniated than the L4-L5 disc on magnetic resonance images. The lengths of iliolumbar ligaments were measured on T1- weighted coronal images. The angles of iliolumbar ligaments were measured on T1-weighted axial images.

Results
The length of iliolumbar ligament was not different between L4-L5 disc herniation and L5-S1 disc herniation. The degree of iliolumbar ligament angle difference (asymmetry of direction) at L5-S1 disc herniation was more deviated in paracentral disc herniation compared with central disc herniation.

Conclusion
The morphology of the iliolumbar ligament, especially its asymmetry of direction, may be a factor influencing the development of disc herniation at L5-S1. (J Korean Acad Rehab Med 2002; 26: 439-444)