Showsight November 2020

FORM FOLLOWS FUNCTION

pictured clockwise from above left: Figure 3A. Well Laid Back Shoulder 45° Figure 3B. Moderately Laid Back Shoulder 30° Figure 3C. Upright Shoulder Blade 20° Figure 4. Scapular Tuberosity A

PHYSICAL EXAM OF THE FOREQUARTERS

The layback of the shoulder blade determines the forward reach of the front leg. The junction of the shoulder blade to the upper arm at the ball and socket joint is referred to as the point of shoulder. This shallow cavity at the bottom of the shoulder blade forms a very shallow socket for articulation with the head of the upper arm (humerus). (See Figures 3A, 3B, 3C.) It is important to note that the ball and socket joint formed where the shoulder blade (scapula) and the upper arm (humerus) meet is not a simple ball and socket type of joint, but is designed for a more sliding movement. This sliding action allows for freer movement in the front assembly and has far less force placed upon it than that produced by the hindquarters. This difference in action is what allows for more lateral movement of the front legs (paddling, winging, etc.) than can be found in the rear assembly. The corresponding ball and socket joint of the pelvis and the hind limb has a very deep cavity and an extremely stable joint that allows it to perform well, even with the stronger force placed upon it by the propulsion of the hindquarters. At the bottom end of the shoulder blade is a beak-like protrusion of bone—the “scapular tuberos- ity.” (See Figure 4.) This tuberosity fits into a corresponding area on the head of the humerus and restricts the forward movement of the humerus and hence the forearm, thus limiting the reach of the forefoot, depending upon the lay- back of the shoulder blade as shown in Figures 3A-C.

It is extremely important to understand that although the rear assembly is attached via the articulation of the upper thigh (femur) at the hip (pelvis) and the pelvis is fused to the sacrum of the spine, the forelimbs of the dog have no skeletal attachment to the chest (tho- rax), only a muscular attachment. The shoulder blade is bound to the body by several broad, flat muscles. At the lower end of the shoulder blade is the upper arm (humerus), which is fairly free in movement, though it is attached to the chest (thorax) by several muscles. The layback of the shoulder blade determines the front reach of the dog. The angulation can be determined when physically examining a dog and depends on certain “landmarks” or points where the bones may be felt through the coat, skin, muscles, and fat of the dog being examined.

140 | SHOWSIGHT MAGAZINE, NOVEMBER 2020

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