Suspensory Apparatus

This consists of the suspensory ligament, sesamoid bones and distal sesamoidean ligaments. These structures together make up the support for the limb from below the knee or hock. The suspensory ligament attaches to the top of the cannon bone, passes down the back of the cannon bone and attaches to the sesamoid bones, which are located behind the fetlock joint. The sesamoid bones act as a fulcrum for the flexor tendons as they run over the fetlock joint. The distal sesamoidean ligaments run from the bottom of the sesamoid bones to the long and short pastern bones.

A traumatic disruption of any of these structures, (i.e. rupture) of the ligaments or fracture of both sesamoid bones, results in a loss of support in the lower limb and loss of integrity of the fetlock joint. This disruption is one of the most common causes of severe ligamentous injuries of the lower limb.

Superficial digital flexor tendon (SDFT): This tendon is the continuation of a muscle group that begins at the back of the elbow. Above and behind the knee, the muscle fibers coelesce to form the SDFT that runs down the back of the cannon region and pastern bones.

The SDFT is the most commonly injured tendon in the equine athlete. The horseman’s term of “bowed tendon” refers to the outward swelling or bowed profile that accompanies tendonitis.

An athletic injury to the SDFT can range from a mild, inapparent strain to a more severe injury with marked lameness. A severe injury may end a horse’s athletic career. Occasionally, a SDFT injury is the result of a single bad step. More often, though, it is due to cumulative minor injuries during training and competition that eventually become extensive enough to cause lameness. With modern ultrasound diagnostics, strains can be diagnosed at an early stage and monitored during the healing process.