Overuse Injuries in the Muscle-Tendon-Enthesis Unit

Overuse injuries of the bone-tendon-muscle unit are a common yet underrecognized source of pain and dysfunction in athletes and the general population. They arise from repetitive mechanical loading and age-related degenerative changes that exceed the adaptive capacity of musculoskeletal tissues. Imaging is central to early detection, accurate characterization, and treatment planning. This review presents a practical, imaging-based framework using magnetic resonance imaging and radiography, emphasizing key diagnostic features, anatomical considerations, and classification. Content is organized into two complementary domains. The first addresses overuse injuries at the tendo-osseous junction, categorized by enthesis type-fibrous versus fibrocartilaginous-and by skeletal maturity, as well as injuries involving fibro-osseous tunnels, pulleys, and bony constraints. The second focuses on myotendinous and intramuscular injury, spanning early edema, fiber disruption, chronic remodeling, and changes related to aging and repetitive microtrauma. This integrated approach supports consistent evaluation across the bone-tendon-muscle continuum.