With improved diagnostic imaging techniques injury to the distal sesamoidean ligaments is becoming recognized as a more common cause of lameness in horses than was previously thought. Most often the oblique (middle) and/or straight (superficial) distal sesamoidean ligaments are involved. Desmitis (strain or sprain) of the deep and and short ligaments is a very rarely diagnosed condition. The location of the distal sesamoidean ligaments is deep to the flexor tendons which makes diagnosis from clinical exam alone difficult. Following localization of the lameness to the pastern it requires ultrasound or magnetic resonance imaging to visualize the damage and it's extent.

This article describes these ligaments and has images of the ligaments to give a better understanding of the anatomy of this area.

This is a view of the pastern and fetlock cut in half but just off the center, this is called parasagital.

Key to Image

Notice you can see a sesamoid bone which would not be seen if cut the pastern right down the middle. It is easy to appreciate here how the flexor tendons and the suspensory unit, consisting of the suspensory ligament, sesamoid bones, and distal sesmoidean ligaments help support the fetlock. Less well appreciated is how this unit, through the action of the distal sesmoidean ligaments, stabilize the fetlock and pastern joints. If you look carefully you can see there are 3 main groups of distal sesmoidean ligaments, colored light blue.