Muscle strains: Pathophysiology and new classification models

Abstract

Muscle strains occur most often at the musculotendinous junction as a consequence of an indirect trauma. Very common in sprinters and jumpers, they usually arise from an indirect trauma, from application of excessive tensile forces. Twojoint muscles, muscles contracting eccentrically and with a higher percentage of type II fi bers, are most predisposed to be injured. However, the coordination and balance between agonist and antagonist muscles, a previous injury, inadequate rehabilitation, and warm up have to be considered as predisposing them. Since structural and biochemical changes occur after the initial insult, the overall goal is to assist the body with its natural healing process, respecting the infl ammatory, repair, and remodeling phases. In an attempt to better defi ne acute muscle strain injuries, we describe an imaging (magnetic resonance or ultrasound) nomenclature, which considers the anatomical site, pattern, and severity of the lesion in the acute stage. This system must be assessed with multiple joints to determine its utility, and additional studies are needed prior to its general acceptance.