Spondylolysis is a defect in the lamina of the vertebrae in the pars interarticularis, usually the fourth or the fifth lumbar vertebrae in the lower (lumbar) spine. Spondylolysis may occur as a congenital defect or be the result of repetitive trauma. Some physicians believe spondylolysis may be caused by genetics, and that someone could be born with thin vertebral bones causing them to be vulnerable to the condition. Spondylolysis is common in teenage gymnasts and football players, and presents with lower back pain that is worse with strenuous exercise or activity. Radiographic findings are subtle, but bone scans, MRI scans, or CT scans will usually detect the lesion. Activity modification, bracing, injections or surgical treatment may be indicated for persistent symptoms.