MRI and US in Hamstring Sports Injury Assessment: Anatomy, Imaging Findings, and Mechanisms of Injury.

Most muscle tears occur in the lower extremities, especially in the hamstrings. The hamstring muscle complex consists of the semimembranosus (SM), semitendinosus (ST), and biceps femoris (BF) muscles. They originate from the ischial tuberosity, and while the BF inserts into the head of the fibula, the ST and SM muscles attach to the medial aspect of the tibia. The hamstrings are primarily hip extensors and knee flexors. Tears mostly occur during sport practice, particularly during forceful stretching or high-speed running, and typical sites are grouped and classified according to their location within the muscle anatomy. Sprint and stretching injuries typically affect the BF and SM, respectively. MRI and US are key complementary modalities for the diagnosis, treatment, and prognosis of hamstring injuries, as injury length, connective tissue involvement, and tear location determine evolution, recovery strategies, and return to play. RSNA, 2025.