Proximal Suspensory Ligament Disease of the Forelimb

At the AAEP Focus meeting in Ft. Collins, Colo., Sue Dyson, VetMB, PhD, FRCVS, head of Clinical Orthopaedics at the Animal Health Trust in Newmarket, England, spoke on proximal suspensory ligament disease (PSD).

She said PSD is common in horses from all disciplines, but is seen particularly in dressage and event horses. In many cases, the lameness might be sudden in onset, but seems to resolve in 24 hours, only to recur when the horse is put back into hard work.

Soft going makes the lameness more noticeable, especially when the injured leg is on the outside of the circle. Slightly intensifying speed at the trot makes the lameness more apparent. In working up the horse on evaluation, it is not uncommon to find that hock flexion amplifies the lameness.

Dyson said there are many possible injuries to the proximal cannon region, and these must be ruled out. Such possibilities include an avulsion fraction at the origin of the suspensory ligament, a palmar cortical fatigue/stress fracture, desmitis of the accessory ligament of the deep digital flexor tendon, superficial or deep flexor tendinitis, middle carpal joint pathology, or osteoarthritis.

Diagnostic nerve blocks can help a veterinarian identify the proximal suspensory ligament as the source of lameness. Radiographs can help determine if there is associated bone pathology that might influence the prognosis for return to athletic soundness. Diagnostic ultrasound performed at two-week intervals can help a veterinarian evaluate healing and progression. The practitioner must link the severity of the lameness with the degree of pathology. However, in some cases, no lesions show up on ultrasound, but might be visible on MRI.

Treatment options for an acute PSD injury rely on rest and controlled exercise. This management is appropriate for 90% of acute lesions. An owner must be careful not to put the horse back to work too soon or under too much stress or this increases the likelihood of re-injury.

Owners should note that, when treated with shock wave therapy, it is possible that the horse's pain will be minimized from the effects of shock wave. This might make the horse appear better than he actually is, creating the potential to bring him back to work too quickly. In chronic cases, extracorporeal shock wave therapy is useful, and repeated treatments might be necessary. Some have reported seeing good results using injections of ACell (urinary bladder matrix) or raw bone marrow injections. Dyson noted that the use of stem cell therapy is not logical for a fibrotic ligament.

About the Author

Nancy S. Loving, DVM

Nancy S. Loving, DVM, owns Loving Equine Clinic in Boulder, Colorado, and has a special interest in managing the care of sport horses. Her book, All Horse Systems Go, is a comprehensive veterinary care and conditioning resource in full color that covers all facets of horse care. She has also authored the books Go the Distance as a resource for endurance horse owners, Conformation and Performance, and First Aid for Horse and Rider in addition to many veterinary articles for both horse owner and professional audiences.

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