Page 126 - Anatomy and Physiology of Farm Animals, 8th Edition

Joints / 111

(carpometacarpal joint) is almost entirely
a plane joint, which allows only very limited
VetBooks.ir gliding movements and makes almost no

contribution to the degree to which the
entire carpus can flex.
The fibrous layer of the joint capsule of
the carpus is extensive, being a long sleeve
extending from the radius to the meta carpus
and enclosing the carpal bones. The synovial
membrane, however, forms three separate
sacs: a radiocarpal sac, a midcarpal sac,
and a carpometacarpal sac.
In the horse, there is normally little
movement between the large metacar-
pal III and the smaller metacarpals II
and IV (splint bones). Excessive move-
ment or trauma results in inflammation
at this site, creating a “splint.” In an
acute state, the splint is a painful swell-
ing where the shafts of the large and
small metacarpal bones meet. Later this
swelling may ossify and form a bony
prominence that may not cause any
lameness at all (Fig. 6‐9).
In ruminants, the third and fourth
metacarpal bones are fused to form the
single cannon bone, which articulates
proximally with the distal carpal bones and Figure 6-9. Dorsal view of equine manus. On
distally with the proximal phalanges. In the left, blue arrows indicate a “splint,” an enlarge-
ment created when the syndesmosis between
dog and pig, the proximal ends of adjacent metacarpal II and III is traumatized. The pink
metacarpal bones abut one another in a arrows on the right show the normal smooth
series of plane joints (intermetacarpal contour of this region.
joints).
The metacarpophalangeal (fetlock)
joint of the horse (Fig. 6‐10) is formed (navicular) bone. The coffin joint is largely
encased within the hoof and is essentially a
by the distal end of the metacarpus; the ginglymus joint. Degenerative joint disease
proximal end of the first phalanx, or long in this joint is commonly referred to as
pastern bone; and the two proximal sesa- low ringbone. A similar pattern of articu-
moid bones. It is a ginglymus joint that in lations is followed for each digit in animals
the normal standing position is hyperex- possessing more than one digit per foot
tended (Fig. 6‐4). (e.g., ruminants and pigs) (Fig. 4‐13).
The proximal interphalangeal (pas-
tern) joint is a ginglymus joint between the
first and second phalanges (the long and Joints of the Pelvic Limb
the short pastern bones). Although it is
a ginglymus joint, it is rather limited in The sacroiliac joint is the only bony
motion. Degenerative changes in this joint connection between the axial and appen-
are called a high ringbone. dicular skeletons. In the young animal,
The distal interphalangeal joint this joint exhibits features of both syn-
(coffin joint) is formed by the second and chondroses and synovial joints, although
third phalanges and the distal sesamoid its mobility is progressively diminished in