To clarify understanding of degenerative suspensory ligament desmitis (DSLD), three strands must be interwoven: (1) To define post-legged conformation, (2) to explain structure and function of the suspensory ligaments and (3) to consider heritability. My purpose is to help you learn to distinguish horses likely to develop DSLD from others.

Post-legged structure is illustrated in photos 1 through 4. The bay mare in photo 1 and the mare in photo 7 have relatively wide open angles at stifle and hock. This defines post-legged structure.

2.  18 year old Arabian mare, Her hind limbs are afflicted with DSLD. As a result of her condition, her fetlocks have dropped (she is coon-footed when weight-bearing), and her stifle and hock angles have been stretched open. The fetlock joints are large, puffy and firm to the touch.

1.  9 year old Arabian mare. She is post-legged but not coon-footed.

The grey mare in photos 2 to 4 is less post-legged, but is severely afflicted with DSLD. This has caused her hind suspensories to become hard to the touch and painful, and has contributed to the evident enlargement of the hock and fetlock joints. Photo 4 illustrates the peculiar stance that the mare typically uses to try to make herself comfortable; bringing one hind foot as far forward as possible, she rests it on the toe. Later she will change legs. The mare walks as much as possible on her toes and avoids weighting her heels.

The branches of the suspensory ligament are arranged around the rear aspect of the fetlock joint so as to suspend it in an elastic sling. In movement, the suspensory sling pushes the fetlock joint up and forward when weight is removed from the limb. At rest it keeps the fetlock joint from descending too far to the ground.

Horses afflicted with DSLD develop inelastic suspensories which do not properly support the fetlock joint. Their conformation becomes what is called coon-footed, with pasterns angled near the horizontal. This dropping of the fetlock causes the distance from the hip socket to the center of the fetlock joint to increase and as a result, straightens the hind limb structure. No matter what hind limb structure a horse may have been born with, as DSLD progresses and the fetlock drops, the horse will become more post-legged and coon-footed.

Now let's consider photo 5. This mare is a full sister to the mare of photo 2. Her hind limb angles are still within the normal range, just as mare 2's were before the onset of DSLD. However, the viewer should note the subtle peculiarity of stance displayed in mare 5's left hind leg. The mare consistently weights only the toe, which may signal the onset of DSLD. Mare 1 and mare 7, who are congenitally more post-legged, do not show this sign. Note that neither mare 1 nor mare 5 is coon-footed with dropped fetlocks.

For these reasons, I do not think that horses should be eliminated from breeding merely on the grounds that they are post-legged or coonfooted. The conformation, by itself, is not enough to show whether or not a horse is a DSLD carrier. For example, generations of post-legged and coon-footed Thoroughbreds have raced without reports of DSLD.

As a matter of fact, post-legged structure is a help to a racehorse, as it predisposes to efficiency in the gallop gait. It's a detriment to any other gait, however, and most especially to amblers who typically coil their loins and round their backs much less than gallopers. Because it rounds its back and coils its loins, a post-legged galloper can bring its hind limbs forward under the body without straining any posterior structure of the limb, but the post-legged Paso horse - at least as it is typically trained and shown - cannot. Certainly, therefore, Paso trainers and showmen should be encouraged to use saddling, bridling, and riding techniques that would help their horse to round their back in movement. A horse with incipient or mild DSLD can be expected to break down faster if ridden with a hollow and stiff back.

Horses that develop DSLD first undergo suspensory ligament degeneration and then show the onset of, or an increase in, structural postleggedness and coon-footedness. There is no question as to what should be done about it: afflicted individuals should be removed from the breeding population. However, to keep this in perspective, I would also remind you that post-legged structure per se is not a desirable characteristic in gaited horses. Postlegged hind limb structure, like every other aspect of conformation, is just as much heritable - just as much caused by genes - as DSLD. The bottom line for gaited horses is therefore simple; Avoid post-legged

3.  A hind view showing the mare's enlarged fetlock joints. Her hocks are also enlarge.

4.  Shows the mare's odd but characteristic stance, resting the hind foot stiffly on the toe.

5.  15 year old Arabian mare. She is a full sister to the mare in photo 4 and she, too, has DSLD but the symptoms are, so far, milder than in her sister. Note the toe-resting stance and compare to photos 1 and 4.

6.  20 year old Peruvian Paso gelding. He is post-legged and coon-footed, with dropped fetlocks, thickened ankles and suspensory ligaments. He is believed to not be affected with genetic DSLD as his condition has been stable for many years and lately has improved, not degenerated.

7.  22 year old Peruvian Paso mare. If this mare has DSLD, it is late in onset and mild in degree. She is congenitally post-legged and probably is not a "carrier". Note the pasterns' angle; there are many sound Thoroughbreds with identical conformation

His condition most likely is the result of an original post-legged conformation and stressful training and riding (with hollow and stiff back and tight neck) as well as improper trimming.

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