Spondylolysis is a relatively common incidental radiographic finding that, most frequently, is asymptomatic. Isthmic spondylolysis with a lesion in the pars interarticularis may be a significant cause of pain in a given individual, particularly in adolescent athletes involved in sports with repetitive spinal motions. The pars lesion likely represents a stress fracture of the bone caused by the cumulative effect of repetitive stress imposed by physical activity. The lesion frequently presents as focal LBP and can often be identified on plain radiography. Advanced imaging with SPECT, CT, and MR imaging may be needed to ascertain the acuity of the lesion, assist in identifying a particular pars lesion as potentially symptomatic, and to exclude other spinal pathology that may be present. Conservative treatment is usually successful in controlling symptoms and restoring function; only a small percentage of patients require surgical intervention for pain or progressive spondylolisthesis. Based on current evidence, treatment requires activity restriction (i.e., temporary discontinuation of the aggravating sport or activity) and may require bracing to achieve treatment goals, although healing, pain relief or both may occur without brace application. A full understanding of spinal biomechanics and pathophysiology, the role of diagnostic imaging, and treatment options is needed to care for these patients.