Imaging of Muscle Sports Injuries

For correct interpretation of the findings on ultrasound and MRI, it is essential to know the microscopic and macroscopic muscle anatomy.The striated muscle, can be considered the largest organ of the body.It represents approximately 25 to 30% of body weight in women and 40 to 50% in men.It consists of two components: muscle fibers and stromal connective tissue.The cell or muscle fiber is the basic structural element.It measures between 10-120 μm.Inside, there are sarcomeres where the actin and myosin filaments are found, responsible for the contraction and elongation of the muscles [1].The individual muscle fibers are grouped into bundles, the fascicles, which are grouped together to form the muscles.They vary in length and transverse diameter depending on each muscle and tend to be similar in size within the muscle.The connective tissue provides the framework to maintain muscle shape in both relaxed and contracted states.Each muscle fiber is surrounded by a delicate network of connective tissue, the endomysium, which contains small vessels, nerves and proteoglycan matrix for ionic and metabolic exchange.Several muscle fibers form a fascicle that is surrounded by a thicker connective tissue, the perimysium that also provides vascularization, innervation and matrix.Several fascicles form a muscle surrounded by an outer layer of connective tissue, the epimysium [2] (Figure 1).