This image from the journal article illustrates the telltale bump on the coronet that indicates a collateral ligament injury. However, Dr. Dyson warns that such visible signs are evident only in a percentage of cases. She recommends scintigraphy or MRI for identifying ligament damage in horses that illustrate specific lameness behavior characteristics.
Sue Dyson's article "Desmitis of the Collateral Ligaments of the Distal Interphalangeal Joint" was very well-received when it was published in Hoofcare & Lameness #79. While it is often difficult to definitely prove that collateral ligament (CL) injury is the sole cause of lameness, particularly in sport horses with degenerative joints and possible multiple foot problems, the good news is that horses do tend to recover from CL injuries.
Recently Sue shared with me her newest paper, which is a retrospective of more than 200 horses that had been diagnosed with lameness related to collateral ligament injury in the foot.
Among the many key points were that there was rarely any outwardly visible sign of injury not could the injury site be palpated or manipulated to induce or replcate the lameness. Trotting in circles on a hard surface was the ideal test. Only occasionally was heat or swelling present. While the injury has now become a common diagnosis for hardworking event horses and jumpers, it may be common in other sports as well.
The horses fell into three groups for comparative study of their diagnostic images, histories, and follow-up, when available.
In a group of 109 selected horses studied for comparison, the medial ligament (73%) was more damaged than the lateral (27%) one; the damage to the ligament was visible on MRIs of all 109 horses. One third of the horses from that sector of the study returned to work. These horses were identified as having lameness caused directly by injury to the ligament, and no other known cause of lameness.
A second group of horses had collateral ligament injury as one of multiple lameness disorders affecting the horse's soundness; these horses had a much poorer prognosis.
A third, smaller group of horses had problems with the ligaments at the point of origin or insertion, but 55% returned to full athletic function.
One of the points made in the paper that is very interesting is the higher incidence of bilateral collateral ligament injury, although the medial is still the more severely affected, in most cases.
A telltale sign of common CL injury in the foot is when the horse is more lame on the outside leg when trotted in a circle on a hard surface.
Whenever possible, Hoofcare & Lameness tries to keep readers up to date with newer research by our authors.
Sue Dyson is a consulting editor of Hoofcare and Lameness and generously shares her articles and photos and cases with us. In Hoofcare 80, she addresses the dilemma of lameness examinations on horses with multiple limb lameness, and suggests guidelines for sorting out horses that are two-legged, three-legged and even all-legged lame.
She is also co-author, with Mike Ross of UPenn, of the reference book Diagnosis and Management of Lameness in the Horse, sold through Hoofcare Publishing.
For more information, see "Desmitis of the Collateral Ligaments of the Distal Interphalangeal Joint" by Sue Dyson MA, VetMB, PhD, DEO, FRCVS in Hoofcare and Lameness Journal, issue #79
"Collateral Desmitis of the Distal Interphalangeal Joint in 233 Horses (January 2001 –July 2006)" published in the Proceedings of the 11th North Carolina State Medical Association, 2006