(2) COLLATERAL LIGAMENTS.--Of these there are two. The =ligamentum collaterale fibulare= (Fig. 60, _j_) is attached to the lateral epicondyle of the femur and passes distad across the tendon of the plantaris muscle to the head of the fibula. Dorsad of the fibular ligament and parallel with it passes the tendon of origin of the extensor longus digitorum. The =ligamentum collaterale tibiale= (Fig. 60, _i_; Fig. 61, _g_) begins on the medial epicondyle of the femur and passes distad to the lateral tuberosity of the tibia; part of it passes one to one and a half centimeters distad of the tuberosity to be attached to a rough ridge on the side of the tibia. [Illustration: FIG. 60.--KNEE-JOINT, FROM THE DORSAL OR PATELLAR SIDE. FIG. 61.--KNEE-JOINT, FROM THE VENTRAL OR FLEXOR SIDE. Fig. 60.--The patella has been removed. 1, femur; 2, tibia; 3, fibula. _a_, patellar surface of femur; _b_, tubercle for attachment of ligamentum patellæ; _c_, medial meniscus; _d_, lateral meniscus; _e_, _f_, ligaments of the menisci; _g_, ligamentum cruciatum anterius; _h_, ligamentum cruciatum posterius; _i_, ligamentum collaterale tibiale; _j_, ligamentum collaterale fibulare. Fig. 61.--The capsule of the joint has been opened. 1, femur; 2, tibia (fibula not shown); 3, sesamoid bone in lateral head of M. gastrocnemius; 4, sesamoid in medial head of M. gastrocnemius; 5, tendon of M. popliteus, with sesamoid bone; 6, 7, lateral and medial condyles of the femur, with the intercondyloid notch between them; 8, 9, lateral and medial condyles of the tibia, with the popliteal notch between them; _a_, _b_, medial and lateral menisci; _c_, ligamentum cruciatum anterius; _d_, ligamentum cruciatum posterius; _e_, _f_, ligaments of the lateral meniscus; _g_, ligamentum collaterale tibiale.] (3) CRUCIAL LIGAMENTS.--There are two of these also. The =ligamentum cruciatum anterius=, or anterior crucial ligament (Fig. 60, _g_; Fig. 61, _c_), is a thick, strong ligament which begins on the dorsal part of the proximal end of the tibia nearer the medial side (Fig. 60, _g_), and passes ventrad and proximad, between the ends of the two bones forming the joint, into the intercondyloid fossa of the femur, and becomes attached to the medial surface of the lateral condyle of the femur (Fig. 61, _c_). It is composed of two partially separated bands, forming a slight angle with one another. It is crossed near its dorsal and ventral ends by two of the ligaments of the menisci. The =ligamentum cruciatum posterius=, or posterior crucial ligament (Fig. 60, _h_; Fig. 61, _d_), begins on the tibia at the edge of the popliteal notch (Fig. 61, _d_), nearer the medial side, and passes dorsad and proximad to be attached to the ventral edge of the patellar surface of the femur, in the intercondyloid fossa (Fig. 60, _h_).