Magnetic resonance imaging features of sacrotuberous ligament partial injury with normal hamstring tendons

The sacrotuberous ligament has an oblique course, from a broad fan-like origin in the posterior superior iliac spine, transverse tubercles of the sacrum and the upper part of the coccyx, descending laterally to attach to the medial surface of the ischial tuberosity. It provides stability to the pelvic girdle, including the sacroiliac joint, counterbalancing its rotation and limiting its movement. Magnetic resonance imaging (MRI) can identify this ligament, depicting its origin, course and continuity with the conjoined biceps femoris and semitendinosus tendon. However, there is no previous report of injuries to the midportion of this ligament, with normal hamstring tendons. In this article, we report three cases of sports-related sacrotuberous ligament injury, with normal hamstring tendons and associated with gluteus maximus muscle strain. MRI demonstrated thickening and irregularities of the sacrotuberous ligament, as well as edema along its fibers and in the adjacent gluteus maximus muscle, with no bone edema and normal tendons. All patients improved with rest and nonsteroidal anti-inflammatory medications.