Page 227 - Canine Lameness

14.2 ­Normal AmaNrmy mAnd oatorari 199

(A) (C) (E) (G)

(B) (D) (F)

Figure 14.2 Normal anatomy of the elbow joint (Note: for all craniocaudal images, lateral is on the left): ELBOW REGION
(A–E) radiographs of canine patients without elbow pathology; (A, B) note that the proximal radial physis is
clearly visible in a 9-month-old dog; (C, D) note the appearance of the proximal radial physis in an adult
dog; (E) note the sesamoid of the supinator muscle (white arrow), a normal structure that is visible in some
dogs and should not be confused with a pathologic condition; and (F, G) normal anatomy of the bones
contributing to the elbow joint: (a) humerus; (b) ulna; (c) radius; (d) lateral humeral condyle (=capitulum);
(e) medial humeral condyle (=trochlea); (f) medial supracondylar crest; (g) olecranon fossa; (h) medial
epicondyle; (i) proximal radial physis; (j) tuber olecranon; (k) trochlear notch; (l) coronoid process of the
ulna; and (m) anconeal process.

the supinator muscle is present and can be identified radiographically (and should not be confused
with a pathologic condition). The coronoid process of the ulna consists of a lateral and medial portion;
pathology of the latter frequently results in lameness. It is in contact with the radius via the radial
incisure (i.e. the notch of the ulna within which the radius can supinate and pronate). The olecranon
fossa, located above the humeral condyles, accommodates the anconeal process during elbow exten-
sion. During development, a large apophysis (i.e. separate ossification center at site of tendon attach-
ment) is visible at the tuber olecranon which should not be confused with a pathologic condition (e.g.
fracture or ununited anconeal process [UAP]). The triceps muscle attaches at the tuber olecranon and
is the major extender of the elbow joint. The biceps brachii muscle inserts on the radius and ulna and
together with the brachialis muscle is one of the major flexors of the elbow joint. Normal range of
motion (ROM) of the elbow joint is approximately 30–160° (Chapter 5). The digital flexor and exten-
sor muscles originate from the area of the medial and lateral epicondyle, respectively. The median and
ulnar nerves are located on the medial aspect of the elbow, with the ulnar nerve being superficial so
that it can be palpated caudally. The radial nerve is located on the lateral aspect of the elbow.
Osteoarthritis (OA) of the elbow joint is generally thought to be the consequence of a primary
problem such as elbow dysplasia (i.e. “secondary” osteoarthritis). One of the most common reasons