Traumatic injuries of thigh and calf muscles in athletes: role and clinical relevance of MR imaging and ultrasound

OBJECTIVES: Magnetic resonance (MR) imaging and ultrasound have become valuable tools for evaluation of traumatic muscle injuries in athletes. Common athletic injuries include strain, contusion and avulsion, which are characterised by muscle fibre disruption, intramuscular haemorrhagic dissection, haematoma at the musculotendinous junction, and perifascial blood or haematoma. METHODS: MR imaging may allow clinicians to predict the time required before athletes can return to competition and the risk of injury recurrence. RESULTS: Fluid-sensitive MR sequences, e.g., fat-suppressed T2-weighted or proton density-weighted turbo spin echo (TSE), and short-tau inversion recovery (STIR) sequences are suitable for detecting oedematous changes in the musculotendinous unit, and for delineating intramuscular or perifascial fluid collections or haematoma. T1-weighted spin echo sequences are used to visualise atrophy and fatty infiltration and to differentiate between haemorrhage/haematoma and oedema. While ultrasound may play a role as an adjunctive imaging method, it is less accurate than MR images for assessing the extent of the injury and it cannot differentiate between new and old injuries. CONCLUSIONS: In this pictorial review, imaging features of lower extremity muscle injuries including strain, contusion and avulsion are reviewed, focusing on MR and ultrasound imaging findings after initial injury and during follow-up, and their relevance in clinical practice is discussed. TEACHING POINTS: • MR imaging may allow clinicians to predict time required before athletes can return to competition • Fluid-sensitive MR sequences are suitable for detecting oedematous changes in the muscles • T1-weighted sequences are used to differentiate between haemorrhage/haematoma and oedema. • Ultrasound can also be used but is less accurate than MR imaging for assessing the extent of the injury