How to Identify Pastern Problems

No single characteristic will tell you that one pastern lump is benign and another is a career stopper. Instead, it's the convergence of characteristics with location and the horse's reaction to it that speaks of the present and long-term implications of the abnormality. The swelling, heat and pain associated with a superficial rope burn on the pastern can be intense enough to cause the horse to limp, yet good nursing care will make the lower leg as good as new. Conversely, a little on-again, off-again choppiness arising from a gradually developing ringbone won't look like much early on but later can mean the end of the horse's usefulness under saddle.

The Bad and Just Ugly
Owners of conformation horses don't want to see even the tiniest nick blemishing their animals' pasterns, but the critical issue for most other lines of work is whether an abnormal lump has or will have soundness implications. The joints are the most likely sites of lameness-associated swellings. Because high ringbone affects a joint with almost no mobility anyway, its prognosis is more optimistic, in many cases, than the outlook for low (within the hoof) ringbone. If articular inflammation eventually fuses the pastern joint (in a process called ankylosis) or if surgery produces the same effect through the use of screws and plates, the horse may return to his previous performance level. However, neither of these "cures" is swift, painless or, in the case of surgical intervention, without risk of complications.

On the other hand, low ringbone is a diagnosis you'd never like to hear for your horse. Given the need for a smoothly operating hinge at the coffin joint and its location within the hoof capsule, swelling, pain and diminished movement there really affect the horse's soundness. Painkillers help control the discomfort, but nothing will reverse the joint restriction, which translates into permanent gait deficits.

Tendon and ligament damage signaled by a soft lump or a hard "filling" on the back of the pastern just above the heels is less common but possibly as debilitating as low ringbone. Strains and tears of the support tissues are quite painful and often more sluggish about healing than bone fractures. Lengthy rest, restricted movement and pain management may encourage resolution of the inflammatory reaction, but injured tendon tissues never regain their previous flexibility and strength. Patience can be rewarding in cases of strained sesamoidean ligaments, which heal to soundness with 12 to 18 months of quiet pasture rest.

When a pastern irregularity does not involve the joint surfaces, tendons or ligaments, it rarely affects the horse's soundness. Scars from accidental injuries--the wire cuts, abrasions, rope burns and such that are so common on horses' lower legs--remain blemishes so long as they involve just the skin and immediate subcutaneous tissues. Wounds that disturb deeper structures, such as the periosteum and joint capsules, trigger calcification in all the wrong places and may or may not affect soundness. You can distinguish the just ugly from the bad by palpating the area: If the scar or lump moves feely over the underlying hard tissues just as the normal, surrounding skin does, it shouldn't limit the horse's movement or cause him pain.

Nonarticular bony lumps rarely are anything but blemishes. The calcification most likely occurred in response to a traumatic event, but, located away from a joint, it doesn't produce pain or impede movement once inflammation has turned to bone.

Rarely does sidebone cause lameness. Ossification of the collateral cartilages may be a normal aging-related change that robs the foot of some of its elasticity. Lateral hoof imbalance and injury of the quarters also produce the characteristic bony ridges just above the coronet. Only when the area is actively inflamed, with signs of heat and sensitivity to pressure, can a lameness possibly be linked to sidebone. Radiographs won't reveal the "truth," as many horses have bony changes in that area without exhibiting any gait changes. If someone points to sidebone in a lame horse, look elsewhere for the cause of the limp.

Preventing pastern injuries is part good management and part wise stock selection. Keeping your horse's lower legs out of injurious entanglements with wire, animal burrows and the like and assuring him sage footing beneath functionally balanced feet will protect him from the majority of pastern-damaging accidents. When selecting or breeding horses for activities high on concussion, quick, lateral moves and abrupt stops, avoid the conformation that makes the pastern vulnerable to breakdown.

For vulnerable horses in risky occupations, train and compete conservatively, and heed the earliest warnings that the joints and support structures are being hit with more stress than they can endure. Better to give the pastern-weary horse a restorative rest, improve his working conditions and maybe even change his occupation. This stretch of anatomy may sport a bunch of bumps and lumps that look worse than they really are in terms of their effects on function, but once the truly serious pastern conditions become entrenched, there's no curing them.

This article originally appeared in the March 1997 issue of EQUUS magazine.