Function, structure, and responses of components of the muscle-tendon unit

A "muscle-tendon unit" is a composite structure that includes muscle, tendon, myotendon junctions, tendon sheaths, and tendon-bone junctions. Each component is unique in its structure, function, response to strain, and associated clinical disorders (usually called "tendinitis"). Tendinitis implies localized tenderness in the distribution of a muscle-tendon unit to palpation, passive stretching, or active contraction. A variety of distinct clinical entities associated with the various components of the muscle-tendon unit are usually grouped together under the term "tendinitis," although each has unique characteristics and etiologic factors. Most have short latencies and favorable prognoses with appropriate clinical management, and most also bear some direct relationship to biomechanical factors, such as compression or strain, as well as to work organizational factors, particularly unaccustomed work.