Spondylolysis is a crack or stress fracture through the pars interarticularis, which is a small, thin portion of the vertebra that connects the upper and lower facet joints. This injury is most common in children/adolescents who participate in sports involving excessive and repeated stress on the lower back.

In some cases, the stress fracture weakens the bone to the point that it can’t maintain its correct position in the spine. This can cause the vertebra to shift or slip out of place, leading to a condition called spondylolisthesis.