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Have you ever asked yourself, “how do I properly sit on my horse?”

Today we’ll look at where we sit on the horse’s back and how the horse’s conformation affects our leg position.

In previous blogs, I’ve explained how the vertebrae are joined together to form a bridge connecting the forelimbs and hind limbs that transmits forces and coordinates movements during locomotion. The vertebral column also forms part of the ribcage that protects the internal organs. The ribcage consists of the vertebrae on top, the sternum or breastbone below, and the ribs curving outward on each side. Inside the ribcage are the heart and lungs, the liver, stomach and some of the intestines. Figure 1 shows the shape of the ribcage as seen from the side.

Figure 1: Skeleton of the horse’s ribcage and upper forelimb seen from the side. The position of the diaphragm is shown in red.

Let’s talk about anatomy and the equine ribcage.

The sternum runs in the groove between the pectoral muscles that form the horse’s chest, passes between the forelimbs and ends a few inches behind the elbow. Behind the elbow, the sternum forms the girth line.

Horses have 18 pairs of ribs, a pair for each thoracic vertebra. The upper part of the rib is composed of bone, but the lower part is made of flexible cartilage that allows some movement.

• Ribs 1-8 are true ribs that attach to the sternum. These ribs are broad and flat so the shoulder blade can glide across them.
• Ribs 9-17 are false ribs which curve outwards to form the horse’s barrel before the lower ends merge together to form the costal arch. These ribs are mobile especially during breathing when they rotate forward and outward, like a bucket handle rotating around the top of a bucket. After cantering up a hill, you may feel the ribcage expand as your horse takes a deep breath
• Rib 18 is a short floating rib that lies within the abdominal muscles on each side. The floating ribs may be different lengths on the left and right sides.