The strong muscle belly of the vastus lateralis inserted at the supero-lateral semi-circle of the patella (Fig. 4). In a fully extended knee joint, fibers of the lateral components of the extensor apparatus were oriented towards the medial superior border of the patella and subsequently towards the medial femoral condyle. Fibers of the medial components of the extensor apparatus were oriented towards the lateral superior border of the patella and subsequently towards the lateral femoral condyle (Figs. 2, 3 and 4).