The principal distinguishing features of the limb skeleton of the pig are the well-developed,

weight­bearing ulnae and fibulae and the complete metapodial and phalangeal complements in the paired accessory digits (Figures 36-1 and 36-4), even though these fail to make contact with firm ground.

The hoofs resemble those of cattle and have a soft digital pad, or bulb, that is well demarcated from the wall and sole (Figure 36-2). The short life span and the common practice of running pigs on concrete make hoof trimming rarely necessary.

The limbs of pigs received little veterinary attention before it was recognized that articular disease (espe­cially osteochondrosis) was relatively common; this stimulated a belated interest in the anatomy of the major joints and in the development of appropriate procedures for their injection. The causation of much articular pathology is uncertain, but suspicion attaches to the demand for rapid weight gain beyond the ability of the immature skeleton to provide adequate support, resulting in articular cartilage breakdown and bone deformities. The use of concrete flooring may also be a factor.