ABSTRACT
TIBIA-FIBULA (FIGS. 44-46) The fibula is always much more slender than its massively built neighbour, the tibia. In some quadrupeds, the fibula is almost en tirely absent and in others it is greatly re duced. The proximal end of the tibia is always the broadest part of the bone. On the relatively flat proximal surface, it bears two shallow, dished articular surfaces, the medial condyle and the lateral condyle, which curve up together in the centre of the proximal surface against the intercondylar eminence. Rising on the cranial side of the proximal end, a promi nent tuberosity runs down the shaft as a crest, giving it a roughly triangular cross section. Where the fibula persists as a sepa rate bone, a small facet for it is tucked into the overhang of the lateral/caudal corner of the proximal tibia. In some of the quadru peds with a greatly reduced fibula, just a vestige is fused on at this point. The distal end of the tibia is swollen, bearing a trough like articular surface for the joint with the talus. The border of this trough on the medial side bulges to distal as a small proc ess, the medial malleolus. In those animals with a fully separate fibula, the end of this bone is also swollen into a lateral malleolus to pair the one on the tibia. Between them, they hold the talus (see below) into its joint.
