[Anatomy and pathology of tendons]

Taking into account its detailed morphology, an attempt has been made to explain a tendon's ability to transmit force between its muscular origin and skeletal insertion. This ability depends upon the aggregation and binding capacity of the molecular elements of type I collagen and is known to decrease with advancing age. The internal structure of a tendon is modified both at the muscle-tendon junction and near its attachment to bone. The very low elasticity of tendinous tissue (about 3% to 8%) is due partly to the texture (pseudo-elasticity) and partly to the molecular composition. The so-called degenerative changes in a tendon begin with deterioration of the internal vascular network and are obviously--so far as its failing capacity is concerned--both initiated and accelerated by the degree of over-loading.