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The term “splint” is often used to describe a condition of interosseous desmitis (or inflamed ligament tissue) occurring between a splint bone and its parent cannon bone. This term a misnomer as it refers to reactive ligament tissue rather than an issue involving the splint bone itself.

Inter = Between
Osseous = Bone
Desmitis = inflammation of ligament tissue


The interosseous ligament courses between the splint bone and adjacent cannon bone and functions to stabilize the junction between the two. Excessive movement of one bone relative to the other can result in compromise (tearing) of interosseous ligament fibers. Inflammation, swelling and pain ensue as a result of this injury. Interosseous desmitis therefore occurs as a result of excessive movement between the splint bone and its parent cannon bone.


What is a splint bone?

Learn More About Splint Bones


“SPLINTS” are very different from “SPLINT FRACTURES”, the latter of which involves the bone proper.

Learn More About Splint Bones


Local inflammation associated with a "splint" may cause considerable focal swelling, which may project inward (axially) towards the center of the limb or outward (abaxially) away from the center of the limb.


Axial Versus Abaxial Splints

Although axial splints are not as common or as visibly obvious as abaxial splints, they pose increased risk for lameness because they may interfere with the movement or function of adjacent soft tissue structures, most critical being the suspensory ligament.

Abaxial splints can be quite unsightly due to their projection under the skin.  Fortunately, however, abaxial splints do not tend to interfere with adjacent tissue and therefore rarely cause long-term lameness.  They are predominantly cosmetic-in-nature.



The Development of a Splint

Initially, injured ligament tissue is relatively "soft".  The "soft" inflammatory reaction associated with a splint lasts for about 10-14 days.

With time and maturity, however, injured ligament fibers often ossify (mineralize), taking on the characteristics of bone rather than soft tissue.  Once ossified, the tissue (and corresponding swelling) is permanent.  The only way to remove it is to "chisel" it out (surgically).




Splints tend to have an acute onset (they appear suddenly). Although they are often painful to the touch, many splints do not result in obvious lameness.

Since the inside splint bone of the horse’s thoracic limb (known as the second metacarpal bone or MC2) experiences the greatest amount of weight bearing load of all of the splint bones, splints are most likely to develop along the inside of the front legs.

They have a characteristic appearance.


Our primary objective during successful treatment of a splint is to reverse the inflammatory reaction and associated swelling before any permanent changes (such as ossification) take place.


Here is a typical course of events during treatment of a “splint”:

1)  DAY 0-10 Post "Splint" Formation.  During the acute phase, we try to suppress local inflammation and swelling as quickly as possible, thereby eluding excessive scar tissue development and eventual disfigurement of the limb.

  • Stall rest ONLY with limited handwalking is permitted during the initial post-injury period.  We want the tissue to "quiet down" without challenging it with any exercise or activity.  As you may have guessed, turnout is NOT permitted during the first 10 days post-injury.

  • Daily application of Ice (15-20 minutes) can be very helpful in the acute stages of splint formation. Click HERE to learn more about cold therapy and its benefits.

  • Daily application of Dexamethasone Sweat Spray is recommended during the initial 10 days to reverse acute inflammation, reduce associated swelling and encourage the injured tissue to "calm down".  In most cases, no over-wrapping is necessary.  Please contact our office for more information on this product, which is made-to-order in the AEC Pharmacy.


2)  DAY 11-14 Post "Splint" Formation.  If the swelling has not completely resolved by this time, we generally recommend intralesional injection of reactive tissue. This works best after the injury site has had an opportunity to quiet down (i.e. after 10 days) but before the reactive tissue ossifies (i.e. before 20 days) and becomes a permanent fixture.


Intralesional Injection of a Splint

The skin around the injection site is surgically prepped. Clipping or shaving of hair is generally not necessary.

A small-gauge needle is placed within the reactive ligament tissue between the splint bone and its parent cannon bone.

A combination of steroid and antibiotic is infused directly into the reactive (swollen) tissue while the horse is standing and sedated. This therapy usually takes about 3-4 weeks to reach its maximum effect.


3)  DAY 15-30 Post "Splint" Formation.  Further stall rest with limited (controlled) exercise is encouraged following intralesional injection of the splint.  Although the medication is very effective at reversing inflammation and reducing swelling, it also "weakens" scar tissue and delays the healing process, thereby predisposing the horse to reinjury. Accordingly, it is not uncommon for splints to recur if the horse resumes exercise prematurely.

We strongly encourage our clients to proceed with caution as they get their horse back to work following splint formation and treatment. Click HERE for Back-to-Work Guidelines.

Pasture turnout is permitted after 30 days post-injury or treatment (if performed).

In some cases, a portion of the reactive tissue ossifies during the healing process and persists despite attentive treatment.  If splint formation results in unsatisfactory cosmetic blemishing (via abaxial swelling) or lameness (via axial swelling), then surgical removal of residual tissue can be performed at the client's request.  This procedure is performed with the horse in lateral recumbency under general anesthesia.

If you have any questions regarding Splint Formation in the Horse please call our office at (678) 867-2577. We look forward to serving you!
THE ATLANTA EQUINE CLINIC: 1665 Ward Road, Hoschton, Georgia 30548 - ph. 678-867-2577

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