Collateral and Dorsal Ligaments
Ligaments found on the lateral and medial aspects of hinge joints are called collateral ligaments. For example, the horse’s left knee (or carpals), has several collateral ligaments, a pair towards the outside (lateral) and a pair towards the midline (medial).
Both lateral collateral ligaments and medial collateral ligaments act together to prevent the joint from moving outside of the normal range of motion (abbreviated as ROM). The combination of ligaments and muscles in most joints provide such well-engineered support that joint dislocation is rare in a horse. Sprains and tearing, however, are still common.
Dorsal Ligament System
The dorsal ligament system is a cooperative trio of ligaments that provide support for the spine, thus affecting posture and the ability to bear weight. The first two parts are the nuchal ligament and the supraspinous ligament, supporting the heavy weight of the head, neck and spine. Two important bursa lie between the ligament and the spine; one at the atlas and another above the T2 spinous process in the wither.
The third part of the dorsal ligament system is the sacral ligaments, which suspend the pelvis and provide attachment sites for some of the large neighboring muscle groups.
The dorsal ligament system functions like the cables of a suspension bridge in the riding horse. (We will discuss this concept further in the practical).