[Blood supply of the quadriceps tendon]

Degenerative changes have been considered to be a cause for spontaneous quadriceps tendon rupture. Aim of this study is to investigate the microvasculature of the quadriceps tendon by injection techniques and immunohistochemical methods (antibodies against laminin) with regard to the pathogenesis of tendon degeneration. The blood supply of the quadriceps tendon arises from descending branches of the lateral circumflex femoral artery, by branches of the descending geniculate artery and by branches of the medial and lateral superior geniculate arteries. Blood vessels penetrate the tendon from the surrounding connective tissue and anastomose with a longitudinally orientated intraligamentous network. Compared to the surrounding synovial layer, the amount of vessels in the tendon substance is greatly reduced. The distribution of blood vessels within the quadriceps tendon is not homogenous. The anterior or superficial part of the tendon has a complete vascular network that extends from the musculo-tendinous junction to the patella. Within the deep portion of the quadriceps tendon there is an oval shaped avascular area which measures app. 30 mm in length and app. 15 mm in width. Within this area the immunohistochemical proof of laminin is negative. An explanation for the absence of blood vessels may be compressive stress caused by the patellar groove which serves as hypomochlion for the quadriceps tendon when the knee is flexed. The occurrence of an avascular zone within the deep layer of the tendon that is directed to the joint cavity may explain the frequency of degenerative changes in this region.