The shaft is covered, except on the linea aspera, by the extensors. The Crureus arises from the front surface for its upper half or a little more, extending up to the front of the trochanter : its origin does not transgress the inner margin, but extends obliquely over the outer margin, an inch or more below the trochanter, to blend with the origin of Vastus externus (Fig. 118). Vastus externus arises as shown in Fig. 120 : its upper fibres are from the front of the great trochanter, and, being aponeurotic, lie as an apparently free edge on the Crureus, although the two muscles are blended at their origins. Vastus internus has a linear origin, therefore, by aponeurosis, from the line shown in Fig. 119, but this only extends as far as the adductor opening : below this level the muscle has origin from the front of the tendon of Adductor magnus, and not from the tone. Thus the inner side of the shaft affords attachment to no muscle, but is covered by the Vastus internus. The upper fibres of the muscle are blended close to the anterior intertrochanteric line with those of the Crureus, wherefore these two muscles, though otherwise separated at their origins, have more or less the superficial appearance of forming one mass.
Subcrureus arises from the inner part of the front surface of the shaft about two thirds of the way down ; its nerve therefore lies on the bone above this level.
A bursa is under the lower end of Crureus in young subjects, joining later with the synovial cavity and so giving it the extension upwards that characterises it : the bursa occasionally remains distinct from the joint.