Page 121 - Anatomy and Physiology of Farm Animals, 8th Edition

106 / Anatomy and Physiology of Farm Animals

forming the joint. Many of the limb joints are types of movement with the exception of
Circumduction combines the other
held in extension during normal standing.
VetBooks.ir the angle between segments is increased rotation; it may be defined as a movement
Hyperextension is movement in which
in which an extremity describes a cone,
beyond 180° (a straight line). The meta- with the distal end of the extremity describing
carpal and metatarsal joints of the horse a circle. A horse that paddles (an undesir-
are hyperextended while in the normal able outward swinging of the feet while in
standing position (often called physiologic motion) is exhibiting circumduction.
hyperextension). Other joints do not Pronation rotates an extremity so that
normally hyperextend unless fatigued or the dorsum is up. Supination is a move-
stressed or when poor conformation ment that rotates an extremity so that the
provides inadequate support to the joint. palmar or plantar aspect of the limb is up.
Hyperextension of the equine carpus, for Pronation and supination are rarely seen to
example, may occur late in a race, when the any extent in farm animals, although dogs
galloping horse is fatigued, and can result and cats are able to pronate and supinate
in injury to the joint. A horse whose carpi their paws to a greater extent.
are hyperextended because of poor con-
formation is said to be calf‐kneed, and it is
prone to go lame with hard work. Types of Synovial Joints
Rotation consists of a twisting move-
ment of a segment around its own axis. Synovial joints can be further described
Shaking the head “no” is a good example of according to the shape of joint surface and
rotation, in this case between the atlas and movements (Fig. 6‐5). Simple joints involve
axis of the vertebral column. only two articulating bones, while composite
Adduction is movement toward the (compound) joints include more than two
median plane. Abduction is movement bones within the same joint capsule. The
away from the median plane. types of synovial joints commonly found in

a b c

f e d

Figure 6-5. Types of joint based on shape and movement. a, saddle joint, not typical of farm animals; b,
pivot joint, e.g., atlantoaxial joint; c, spheroid joint, e.g., coxofemoral joint; d, condylar joint, e.g., femo-
rotibial joint; e, hinge joint, e.g., elbow; f, plane joint, e.g., intercarpal joints.