A 21-year-old collegiate gymnast presented with midline pain at the thoracolumbar junction upon back extension and a "gritty" sensation at that level. Ultrasound revealed an area of hyperechogenicity, representing a calcification, within the interspinous ligament at the area of maximal tenderness at the T12-L1 level. Under ultrasound guidance, multiple fenestrations were made into the calcification and a mixture of lidocaine and triamcinolone was injected. The patient experienced immediate improvement in her symptoms, and resolution occurred during the subsequent 6 weeks; she was able to make a gradual return to gymnastics. Interspinous ligament calcification in a young athlete has not been previously reported.