I’m 55-years old, postmenopausal, and now discovered I have something called degenerative spondylolisthesis. What is this and what causes it?

Normally, the bones of the spine (the vertebrae) stand neatly stacked on top of one another. Ligaments and joints support the spine. Spondylolisthesis is a condition that alters the alignment of the spine. One of the vertebral bones slips forward over the one below it. As the bone slips forward, the nearby tissues and nerves can become irritated and painful.

In younger children and teens, spondylolisthesis develops as a result of excessive or repeated strain on the pars interarticularis of the vertebrae. A crack or bone fracture forms in the pars, which is part of the bony ring on the back of the spinal column. At first the fracture remains stable and the bones do not separate. That condition is referred to as spondylolysis. But if the bones separate at the fracture site, and the vertebrae slips forward, it creates the condition called spondylolisthesis.

Older children and teens whose bones are still growing are at greatest risk for this condition. Low back pain in athletes with spondylolysis may be more common in football players, gymnasts, wrestlers, weightlifters, and volleyball players.

But older adults can also develop a degenerative form of spondylolysis that can progress to become spondylolisthesis. Most of the time (in adults and children), the defect is present on both sides. In older adults, degeneration of the disc and facet (spinal) joints can lead to spondylolisthesis.

Facet joints are small joints that connect the back of the spine together. Normally, the facet joints connecting L5 to the sacrum create a solid buttress to prevent L5 from slipping over the top of the sacrum. However, when problems exist in the disc, facet joints, or bony ring of L5, the buttress becomes ineffective. As a result, the L5 vertebra can slip forward over the top of the sacrum.

Spondylolisthesis from degeneration usually affects people over 50 years old. This condition occurs in African Americans more often than in whites. Women are affected as much as three times more often than men. The effect of the female hormone estrogen on ligaments and joints is known to cause laxity or looseness. The higher levels of estrogen in women may account for the greater incidence of spondylolisthesis. Degenerative spondylolisthesis mainly involves slippage of L4 over L5.