The shaft is nearly straight and cylindrical. A rough line is continued along its ventral surface from the lesser trochanter, and a similar line along its lateral surface from the greater trochanter; these unite ventrad to form the =linea aspera= (_h_). On its ventral surface is a nutrient foramen, directed proximad. The shaft gradually widens distad and ends in two =condyles= (_i_ and _j_) which are continuous dorsad but separated ventrad by a deep notch, the =intercondyloid fossa= (_k_). The distal surface of the shaft and condyles is articular. This articular surface is larger on the lateral condyle (_j_). The part of the articular surface on the end of the shaft (=patellar surface=) is for the patella; that part of it on the condyles and separated by the notch is for the tibia. On the lateral surface of the lateral condyle is a slight prominence, the lateral epicondyle (_l_), and on the medial surface of the medial condyle is another prominence, the medial epicondyle; both are for the attachment of ligaments. =Patella= (Fig. 1, _r_).--The patella is a small flat bone with a pear-shaped outline, having its apex distad. It lies against the articular surface at the lower end of the shaft of the femur. It thus covers the knee-joint. The inner surface is smooth and convex from side to side, but concave in a proximodistal line. It fits against the lower end of the femur. Its outer surface is rough and concave. It is a sesamoid bone inserted in the tendon of the quadriceps femoris muscle. Three other sesamoid bones are found in the region of the knee (see Fig. 61, p. 89). Two are in the tendons of the gastrocnemius muscle, proximad of the two condyles of the femur. The third is in the tendon of the popliteus muscle, just laterad of the lateral condyle of the femur. [Illustration: FIG. 57.--TIBIA AND FIBULA OF LEFT LEG, DORSAL VIEW. _I_, tibia; _II_, fibula. _a_, medial condyle of the tibia; _b_, lateral condyle; _c_, spine of the tibia; _d_, crest of the tibia; _e_, tubercle for attachment of the patellar ligament; _f_, medial malleolus; _g_, projection of dorsal surface of the tibia; _h_, head of fibula; _i_, lateral malleolus.] =Tibia= (_I_, Fig. 57).--The tibia is the longer of the two bones of the leg between the knee and the ankle, and is the longest bone of the body. It has a triangular shaft and enlarged proximal and distal ends.