What is Suspensory Ligament Strain?
A broad, thick, elastic, tendon-like band that starts at the back of the cannon bone and connects to the pastern bone, the suspensory ligament is one part of the suspensory apparatus of the horse’s leg. It splits into two branches (medial and lateral) that encircle and enclose in part, the sesamoid bones. Smaller branches exist as well and join to the major extensor tendon of the horse’s limb. The suspensory ligament’s main purpose is to make sure that the fetlock joint does not overextend during the weight-bearing point in the horse’s stride. The suspensory apparatus functions as a spring that assists in supporting the weight of the horse as well as a shock absorber for his legs.
When there is damage to the ligament or any of its branches, it is known as suspensory desmitis. These injuries are due to there being too much strain on the ligament while the horse is participating in strenuous exercise. When there is a large load placed on the fetlock during exercise as well as the flexor muscles being fatigued, it can lead to the fetlock overextending. This overwhelms the structures that are meant for support, to include the suspensory ligament. When the suspensory ligament is overstretched it can result in damage to the fibers either at the origin, body or branches.
Suspensory ligament injury occurs when there is damage to the suspensory ligament, which starts at the back of the cannon bone and connects to the pastern bone below it.
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Symptoms of Suspensory Ligament Strain in Horses
Should your horse experience a suspensory ligament injury, you may notice the following:
- Lameness that can vary from mild that comes and goes through ongoing and severe.
- Particularly in cases of repeated injury, a thickening of the area of the leg that is impacted
- Warmth and tenderness
- The fetlock may collapse toward the ground in the case of the ligament rupturing
Types of suspensory ligament injury include:
Proximal Suspensory Desmitis
This is an injury occurring near the origin of the suspensory ligament at the top of the back of the cannon bone. Injuries like these can be hard to notice at first because this part of the suspensory ligament is located under the deep digital flexor tendons and is not easy to touch or to notice the presence of heat or swelling. You may initially notice slight lameness or lameness that occurs off and on.
Suspensory Body Desmitis
The suspensory ligament body is between the proximal quarter of the ligament and the place where it splits into the medial and lateral branches. Injuries to this portion of the ligament are more likely in the foreleg of the horse and typically present with heat, swelling and pain when touched. While lameness may not be seen right away, as damage continues the symptoms will progress if the horse continues his activity. This is likely the most common type of injury to the suspensory ligament. In many cases the injury becomes chronic because early on in the course of the injury the horse is able to continue to function. Chronic injury will lead to the ligament becoming more and more thick, ultimately pushing on the splint bones, which can cause fractures.
Suspensory Ligament Branch Injuries
Injury to one or both of the suspensory ligament branches occurs often in athletic horses. This is not hard to notice as swelling can be easily seen and the area where the injury is located is sore to the touch. These injuries occur suddenly and may be in conjunction to a fracture or injury to the proximal sesamoid bones where they attach to the suspensory branches.
Distal Sesamoidean Ligament Injuries
These injuries can be joined by avulsion fractures of the sesamoid bones as a result of the pull at the origin attachment of the ligaments. These ligaments can rupture while a horse is racing and cause displacement of the sesamoid bones.
Causes of Suspensory Ligament Strain in Horses
When too much stress occurs on the suspensory ligament apparatus when the horse is jumping or moving at fast speeds it can cause the ligament to over-stretch and the fibers that are connected to the sesamoid or cannon bones may tear. The severity of the tear will depend upon how much damage has been done to the fibers that have been torn.
Diagnosis of Suspensory Ligament Strain in Horses
Injuries to the suspensory ligament are not unusual, however they often go undiagnosed or are misdiagnosed for some time. In many cases there is little or no swelling that is able to be seen in the limb and lameness may come and go and be relatively minimal, resolving itself after rest. Your veterinarian will conduct a lameness examination of your horse; in some cases, he may observe swelling or pain, in others he may not. Your veterinarian may observe your horse walk and trot on a straight line and canter circles. Examining your horse on hard and soft footing and under saddle may be helpful for the veterinarian to get an idea of what may be impacting your horse.
Once your veterinarian feels that the pain is coming from the suspensory ligament area, diagnostic imaging will be utilized, however it will likely be necessary for your veterinarian to perform diagnostic nerve blocks to find where the source of pain is within the area. If suspecting a suspensory ligament injury, your veterinarian will want to verify that when the area of the ligament is frozen, the gait of your horse changes. Ultrasound may also be used to understand the seriousness of the injury in your horse.
Treatment of Suspensory Ligament Strain in Horses
Once your veterinarian understands the injury your horse is experiencing, he will determine a course of treatment. Should the damage to his suspensory ligament be limited to the cannon bone attachment, anti-inflammatory drugs like corticosteroids may be given to your horse by injection in order to reduce inflammation. Cold hosing and icing may be recommended for one to two weeks after diagnosis. Your veterinarian may also consider corrective shoeing to increase the height of your horse’s heel and lessen tension on the ligament that has been damaged. Taking a break from hard training will likely be recommended, though your horse can continue daily walks. Some veterinarians use electromagnetic machines as part of their treatment program for soft tissue injuries of the suspensory ligament.
Should your horse not show improvement with these treatments, shock wave therapy can be utilized. While your horse would have to be anesthetized, it has a high success rate.
Recovery of Suspensory Ligament Strain in Horses
If your horse experiences a suspensory ligament injury, follow up appointments will likely be necessary so that your veterinarian can check on your horse’s progress and confirm that treatment is effective. It will be important to work closely with your veterinarian to ensure the best outcome for your horse.
Suspensory Ligament Strain Questions and Advice from Veterinary Professionals
My horse has a squishy-ish lump on his left front leg on the outer side, a little under is knee. Two weeks ago I spotted this, but it was the day I came back to him after a week of being away. He was lame under saddle, didn’t want to work, but shows no signs of pain from touch. Leg was hot for about two days, no longer is. Normal body temperature. He doesn’t look lame on ground, no change in his personality or attitude. No change in the size of the lump since I first noticed it. He has been on stall rest for two weeks now, standing wraps nightly, zero riding, and cold hosing daily. I can’t call a vet until next week, unfortunately, so I am just looking for some advice or help on what to do. Not sure if this video will be helpful, but it shows where the squishy-ness is: https://youtu.be/Ch1qJAT-4b4
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