The knee joint blood supply is derived from a rich anastomosis of the five major constant arteries, namely, the superior medial and lateral, the middle (posterior), and the inferior medial and lateral genicular arteries. Anastomosis also occurs with descending genicular arteries and the anterior tibial recurrent artery. These branches form anastomoses in and around the knee joint, while each major vessel was noted to provide the respective major blood supply to specific areas. The most obvious difference between vascularization of child and adult knees was the separation of vessels and relative avascularity of epiphyseal plate areas; such persisted until closure of the epiphyseal plate. The regions representing the seals of plate closure had less rich vascularization. A rich intraosseous blood supply was defined in the femoral and tibial condyles and the patella. Similarly, the adjacent and superficial soft tissues, including major ligaments and peripheral parts of the menisci, were richly vascularized. Areas of separated vascularization in children may have relevance to epiphyseal injury, growth deformity, Osgood-Schlatter disease, and hematogenous osteomyelitis. In adults, such information may be relevant to high tibial osteotomy, meniscus and cruciate ligament repair, and surgery utilizing the semitendinosus tendon, fascia lata, or patella tendon grafts.