Sacral stress fractures: tracking down nonspecific pain in distance runners.

Sacral stress fractures are an underrecognized cause of low-back and gluteal pain in distance runners. The combination of low bone density and increased activity blurs the boundary between fatigue and insufficiency fractures in many runners. MRI is the preferred radiologic technique because of its ability to localize the site of injury and rule out tumors, disk disease, or sacroiliitis.