Suspensory Ligament Injury in a Horse

Suspensory injuries can occur to horses in any discipline.

A horse's equine suspensory ligament helps support the fetlock joint and absorb shock. It starts at the back of the knee and runs down the cannon bone, attaching to the fetlock on the back of the horse's leg. A suspensory injury can range from a mild strain to severe tears of the ligament. These injuries can occur in any equine breed or discipline, but are most common in horses involved in athletic events like racing, cutting and jumping.

Anatomy

The suspensory ligament works with the sesamoid bones and distal sesamoidean ligaments to form the suspensory apparatus, which prevents the fetlock from hyperextending. Suspensory injuries are defined by their location within the ligament:
• Proximal--the beginning of the ligament at the back of the cannon bone
• Body--the area just below the proximal area ranging to just above where the ligament branches off
• Branch--the medial and lateral branches of the ligament
• Distal--the spot where the branches attach to the fetlock

Causes

Improper hoof balance can contribute to suspensory ligament injuries.

Overextension of the fetlock joint can damage the ligament and can happen during high-speed or strenuous activity. Fatigue also makes the ligament more susceptible to overextension. Poor hoof balance and deep arena footing can also contribute to suspensory injuries. Uneven hoof balance--when one side of the hoof wall is longer than the other--puts unnecessary strain on the suspensory ligament. Proper trimming and shoeing by an expert farrier is vital to prevent uneven hoof balance. Deep footing--where the dirt is soft and more than four or five inches deep--can invite fetlock overextension and suspensory injuries.

Diagnosis

Suspensory injuries are usually diagnosed by ultrasound. A veterinarian needs to read the ultrasound and make a professional diagnosis, but owners can also see the injury on the ultrasound. Normal ligaments appear white with long and unbroken fibers, while injured ligaments show up as grey or black areas with an uneven fiber pattern. Proximal and distal suspensory injuries are difficult to diagnose because of their locations and may require diagnostic nerve blocks and/or nuclear scintigraphy to fully assess their impact. A diagnostic nerve block involves injecting a numbing agent into the lower leg at strategic locations to determine where the pain is. Nuclear scintigraphy is a bone scan that will show inflammation within the bone via a gamma camera image and injection of a radio-isotope.

Treatment

Stall rest is part of the healing program.

Treatment of a suspensory injury depends on the extent of the injury. Suspensory injury treatments may include one or more of the following:
• Walking the horse by hand and stall rest
• Using ice and cold water therapy
• Cold laser treatment
• Corrective shoeing
• Hyaluronic acid or corticosteroid injections. Hyaluronic acid is a binding, lubricating and protective gel.
• Electromagnetic therapy

Prognosis

Many horses return to work after a recovery period.

With proper diagnosis and rehabilitation, horses can recover from suspensory injuries. After 60 days of treatment, the injury can be re-checked via ultrasound to evaluate its status. Often, horses can slowly return to work before the ultrasound shows healing. Reinjury to the ligament can occur if the ligament is not given enough time to repair or if the horse is returned to work too quickly.

References

• Vet Med: Suspensory Ligament Injuries in Horses
• Thoroughbred Times: Treating Suspensory Ligament Injury
• Virgina Equine Imaging: Nuclear Scintigraphy

Resources

• The Horse: Guide to Horse Health Care