Q: I have an 11-year-old Welsh Pony gelding that I have competed in combined driving events. Over a year and a half ago, I noticed a limp starting on his right front. A veterinarian diagnosed it as an annular ligament strain. My pony has been given steroid injections, put on an oral hyaluronic acid supplement and occasionally bute, and taken to a high-priced shoer, but his lameness has only worsened until it is now very evident.

Ultrasounds showed a “thickening of the annular ligament,” which has now become visible as a kind of knobby protrusion on the back of the right fetlock joint. My veterinarian has discussed the possibility of surgery, which I unfortunately cannot afford. 

This pony is my pride and joy and one of the bright spots in my life. I would be satisfied showing him in only the dressage driving shows and forgoing the marathons if I could get him that sound. Should I continue with the shots, even though they’ve done little good so far? Could you please tell me what if there are any other real solutions for this condition?Marlene Giaconmetto; Wellington, Nevada

A:The palmar annular ligament is the tough, fibrous band that wraps horizontally around the back of the fetlock joint; the long flexor tendons, which run down the back of the leg, pass though a narrow canal underneath the palmar annular ligament, which holds them in place over the sesamoid bones.

Desmitis (inflammation) of the palmar annular ligament can be a difficult injury to diagnose and treat in horses. Injury to the ligament apparently occurs in two main ways: The first is a direct injury to the ligament from some sort of external source, such as overreaching, or interfering, from the rear hoof. When this happens, the thickening of the annular ligament will constrict the space through which the flexor tendons run. This will, in turn, pinch the tendons as they slide back and forth, resulting in pain and possibly secondary injury to the tendon.

The second form of injury to the palmar annular ligament begins with chronic injury and inflammation of one of the underlying tendons and the digital flexor tendon sheath. In this case, the injury may result in an enlarged tendon that does not have room to move through the space beneath the annual ligament. Over time, this situation will result in inflammation and injury in the overlying ligament as well.

Either way, it is important to treat all of the injuries in order to be successful. Injecting the tendon sheath with anti-inflammatories is a good start in most cases, and this treatment is usually followed by a program of rest and rehabilitation.

If this does not help the horse enough, or there is dramatic thickening of the ligament, then transecting (desmotomy) of the ligament is usually necessary to give the tendons room to move without pain. When the ligament is cut surgically, the space in which the tendons run is enlarged, leaving them more space. The ligament will heal back together, but it should end up being longer to allow room for movement.

In chronic cases, the ongoing inflammation can cause adhesions to form within the tendon sheath, which will need to be transected (cut) so that they do not cause pain. Post-operatively, horses need to be rehabilitated with active motion to keep adhesions from forming and to keep the annular ligament as long as possible while healing.

Unfortunately, even with surgery, only about 65 percent of these horses become completely sound for athletic use, and some will require additional injections. If there is a tendon injury, that will need to be addressed as well and may require debridement at surgery, additional rest and sometimes additional therapy to heal such as stem cells, platelet-rich plasma, extracorporeal shock wave therapy, etc. With concomitant tendon injury and adhesion, the horse’s long-term prognosis could go down accordingly.

In any case, palmar annular ligament desmitis can be very challenging to treat. Some of these injuries will respond really well to treatment, while others become chronic nagging problems. The only way to tell which your horse will be is to treat it aggressively and hope for the best.

Chad J. Zubrod, DVM, DACVS
Oakridge Equine Hospital
Edmond, Oklahoma