Splints

Splints in horses are bony growths that form on the splint bones, which are the smaller bones that run along the sides of the cannon bone in the lower leg. The condition develops when the interosseous ligament that connects the splint bone to the cannon bone becomes inflamed or damaged, and the body responds by creating bony growth. Splints are one of the most common problems seen in young horses, particularly those involved in training or performance.

What makes splints relatively common and somewhat expected in horses is that they're largely a consequence of work and the stress young bones experience as horses are trained and ridden. Most splints develop in horses under ten years old, with the highest incidence in horses being actively trained. They're significantly less common in older horses or those not being worked. This pattern suggests that splints are related to the demands of training and work on immature skeletal structures.

Many splints cause lameness and swelling during their active phase, but once they've ossified and become stable, horses often move sound and function normally despite the bony growth being present. Some horses have splints that never cause lameness. Others develop splints that cause chronic problems. Understanding the difference between a splint that's simply an incidental finding and one that's actually causing functional problems helps you make appropriate management decisions.

The good news about splints is that they're not a permanent career-ending problem for most horses. Many horses with splints continue working and performing perfectly well. The key is recognizing the condition, managing it appropriately during the active phase, and returning to work gradually to avoid re-injury. Understanding splints helps you take a balanced approach—not over-reacting to a minor splint while also properly managing problematic ones.

This guide covers what splints are, what causes them, how to recognize them, what management options exist, and what realistic outcomes look like for horses with splints. Understanding splints helps you work effectively with your veterinarian to manage a horse with a splint and make informed decisions about work and activity.

The primary cause of splints is repetitive stress and concussion on the lower leg structures during work. Young horses, whose bones are still maturing and whose skeletal structures are still adapting to work demands, are particularly vulnerable. The splint bones connect to the cannon bone via an interosseous ligament. Stress on this ligament from work, jumping, or training on hard footing causes inflammation and damage to the ligament. The body responds by forming bone, attempting to stabilize the area—this is the splint formation.

Age is the most significant factor in splint formation. The vast majority of splints occur in horses under ten years old, with peak incidence in young horses being actively trained. Horses in their early training years, being ridden for the first time, or undergoing serious training are most prone to splints. As horses mature and their skeletal structures fully ossify, splint formation becomes much less likely. This age relationship confirms that splints are related to the stress of work on developing skeletal structures.

Type of work influences splint development. Horses involved in jumping, racing, or other high-impact activities develop splints more frequently than those doing light riding. Longeing is a known risk factor for splint formation, likely because the circular motion and impact on the inside of the leg puts significant stress on the splint bone. Young horses in intense training programs develop splints more often than those with lighter work schedules.

Training errors contribute to splint formation. Young horses trained too intensely, too quickly, or on hard footing develop splints more readily than those with gradual training progressions on softer ground. Improper training that puts excessive stress on young structures, such as excessive longeing or jumping young horses before they're ready, contributes to splint formation.

Footing significantly influences splint risk. Horses worked repeatedly on hard surfaces like pavement or hard-packed ground develop splints more frequently than those with access to softer footing. This is why many training programs prioritize arena work and softer ground. The impact of hard footing puts stress on the lower leg structures that soft footing doesn't create.

Conformation plays a role in splint formation. Horses with certain leg alignments, base-wide or base-narrow stances, or other conformation variations seem predisposed to splints. Horses with naturally good straight leg conformation are somewhat more resistant to splints than those with conformation faults, though splints can occur in any conformation.

Genetics might influence splint susceptibility. Some horses seem prone to splints while others never develop them despite similar work and training. This might reflect inherited factors affecting bone quality, ligament strength, or healing response to stress. Horses with parents that had splints might be more prone to them, though this correlation isn't absolute.

Trauma sometimes triggers splint formation. A direct blow to the leg, a horse stepping on themselves, or minor trauma sometimes initiates splint formation. These acute injuries differ from the chronic overuse that causes most splints but can result in similar bony growth.

Swelling on the medial (inner) or lateral (outer) aspect of the leg, typically in the lower third of the cannon bone, is the most obvious sign of an active splint. The swelling is firm and bony rather than soft and puffy. It appears suddenly or develops gradually, depending on how the splint formed. Swelling from a developing splint might be warm to the touch and somewhat painful, while older, stable splints often feel cool and cause no pain.

Lameness during the acute phase of splint formation is common. A horse might develop sudden-onset lameness after work or training, particularly if the splint formed from acute trauma. Alternatively, lameness might develop gradually over weeks if the splint is forming from chronic stress. The degree of lameness varies—some horses are mildly lame while others show more significant lameness initially.

Heat in the affected leg, felt as warmth compared to the opposite leg, indicates active inflammation. Active splint formation produces visible heat in the area, while older, healed splints feel cool. The presence of heat suggests ongoing inflammation and active bone growth.

Response to work and activity helps assess whether a splint is causing problems. A horse with an active, painful splint might be reluctant to move, moving stiffly or with visible lameness. A horse with a well-healed, painless splint might work perfectly normally despite the bony growth being present. Working gently and observing your horse's response helps you assess whether the splint is causing functional problems.

Palpable bony growth on the leg is felt as a hardened lump along the splint bone location. A fresh splint might still feel somewhat swollen and warm. Older, stable splints feel like discrete, firm bony growth. Running your hands along your horse's lower legs regularly helps you notice splints early before they cause obvious problems.

May respond to flexion tests on some cases. Flexing the leg or a splint test specifically designed to stress the splint bone area sometimes causes lameness if the splint is active and painful. However, many horses with splints don't show obvious response to flexion tests, so negative test results don't rule out splints.

Your horse might show reluctance to turn sharply or move in certain directions if the splint is on the side that experiences stress from turning. A splint on the inside of one front leg might cause the horse to move stiffly in one direction while turning the opposite direction seems less problematic.

Diagnosis of splints begins with physical examination and palpation of the area. Your veterinarian will feel the leg carefully, identifying any swelling, heat, or bony growth. Palpation helps determine where exactly the splint is located and whether it's in an active phase causing heat and swelling or is a stable, healed splint. Lameness evaluation helps assess whether the splint is causing functional problems or is just an incidental finding.

Radiographs confirm diagnosis and assess the extent of bony growth. Radiographs show the bone clearly, allowing your veterinarian to see the splint formation and assess whether it's in an early stage of formation, actively growing, or fully ossified and stable. Radiographs also help rule out other problems that might be causing similar signs. Multiple radiographic views are sometimes taken to fully assess the splint.

Ultrasound sometimes provides additional information about soft tissue involvement and the extent of inflammation around the developing splint. Ultrasound shows the interosseous ligament and associated soft tissue, helping assess the degree of ligament damage and inflammation present.

Treatment of active splints focuses on reducing inflammation and pain while allowing the body to complete the healing process. Rest is the primary treatment—the horse should be given time off work to allow inflammation to resolve. The amount of rest needed depends on the severity of the splint, with mild splints sometimes improving with a few weeks of rest while more severe splints require several months off work.

Ice or cold therapy applied to the area during the first week or two after acute splint formation helps reduce swelling and pain. Ice applied repeatedly during the day, for 15 to 20 minutes at a time, helps minimize inflammation. After the acute phase, some horses benefit from heat application instead.

Compression wrapping provides support to the affected area and helps reduce swelling. Carefully applied compression wraps, sometimes combined with topical treatments, help manage swelling and provide support. Your veterinarian or farrier can demonstrate appropriate wrapping if beneficial for your horse.

Anti-inflammatory medications like phenylbutazone reduce inflammation and pain during the active phase. These are typically used for the first week or two after acute splint formation. NSAIDs help manage pain and inflammation, allowing your horse to be more comfortable while healing progresses. Long-term NSAID use is avoided due to potential side effects with prolonged use.

Activity management is crucial—the horse should be rested from work while the acute inflammation resolves. The amount of restriction depends on the severity of the splint and how lame the horse is. Some horses benefit from hand-walking to maintain circulation and prevent stiffness, while others need complete stall rest. Your veterinarian will recommend appropriate activity levels for your specific situation.

Progressive return to work begins weeks after initial rest, once inflammation has resolved and heat is gone from the area. Hand-walking begins in short sessions and gradually increases. Trotting is reintroduced carefully, with work intensity increased very gradually. Rushing return to work before the splint is fully healed causes re-inflammation and can perpetuate the problem indefinitely.

During the acute phase of splint formation, management focuses on minimizing inflammation and pain. Ice application several times daily, compression wrapping, and appropriate medication help manage the acute problem. Rest from work is essential—the horse shouldn't be ridden or worked at all during the acute phase. Hand-walking might be permitted depending on the severity of lameness, as some gentle movement can help with circulation without stressing the injured area.

Stabling should be clean and safe, with adequate bedding to provide comfort. Concrete floors should be avoided in favor of bedded surfaces that reduce concussion. The horse should be confined enough to prevent running or rough movement that might re-stress the area, but allowing movement in a small area is often better than complete immobility.

Feeding and nutrition continue normally during splint management. Some owners give supplements thought to support bone and soft tissue healing, like MSM or amino acids, though scientific evidence for these supplements is mixed. Adequate protein and minerals support healing, so ensuring your horse receives complete nutrition is important.

Pain management continues for weeks with medication as needed, particularly during the acute phase. As inflammation resolves, medication can be reduced and discontinued. The goal is keeping your horse comfortable without prolonging medication unnecessarily.

Monitoring the splint during healing helps track progress. Regular palpation to assess when heat resolves and swelling decreases helps you know when it's safe to begin increasing activity. Initially decreasing swelling and heat that then returns suggests you're progressing activity too quickly and should back off.

Progressive return to work must be gradual. After an initial rest period, hand-walking begins in short sessions—perhaps 10-15 minutes—and gradually increases over weeks. The horse should show no lameness and the area should remain cool and not swollen before advancing activity. Once hand-walking is going well, light trotting might be permitted briefly, with gradual increases as weeks pass. Most horses need 6-12 weeks or more of controlled activity progression before returning to full work.

Monitoring for recurrence is important. If swelling or heat returns when increasing activity, this suggests the splint isn't fully stable yet and you need to return to a lower level of activity. Going slowly prevents multiple sets of acute inflammation that can perpetuate problems indefinitely.

Prevention of splints involves managing young horses appropriately during training. Gradual training progressions that build fitness and strength gradually, rather than subjecting young horses to intense work immediately, reduces splint incidence. Young horses need time for their skeletal structures to develop and adapt to work demands. Training programs that incorporate rest days, avoid excessive impact work on hard surfaces, and build fitness gradually minimize splint risk.

Providing soft footing for training reduces impact stress that contributes to splint formation. Arena work on soft ground, pasture work, or other low-impact footing is preferable to repeated work on hard surfaces. When hard footing is unavoidable, minimizing work intensity and duration helps. Horses trained primarily on softer footing develop fewer splints than those working on hard ground repeatedly.

Managing work appropriately helps prevent splints. Young horses shouldn't be longeing excessively or jumping before they're physically mature and adequately trained. High-impact activities should be limited in young, developing horses. Building fitness and strength through appropriate training prevents stress injuries that might lead to splints.

The prognosis for splints is generally good. Most splints, once healed and fully ossified, cause no ongoing problems. Horses return to normal work and function despite the bony growth being visible on radiographs. Many horses have splints that cause no lameness at all—the splint is simply an incidental finding on radiographs.

Some horses do develop chronic problems from splints, remaining slightly lame or moving unevenly even after the acute phase resolves. These horses require ongoing management and activity modifications. Some horses develop splints on both front legs or recurrent splints in the same location, requiring more careful long-term management.

Horses that have had splints are at increased risk of re-injury in the same location or developing splints in similar locations. Once a horse has had a splint, careful management and appropriate conditioning help prevent recurrence. These horses often benefit from ongoing soft footing preferences and careful progression of work intensity.

Long-term quality of life for horses with healed splints is typically normal. Most horses are eventually able to return to work and perform at previous levels. Some might have slight permanent bony enlargement visible, but functionally they move and work normally. Even horses with slight ongoing stiffness from splints often go on to successful careers in whatever discipline their owners pursue.

Accepting that splints might occur as part of training young horses, managing them appropriately when they develop, and progressing return to work gradually helps maximize the likelihood of a good outcome. Most horses with splints have completely normal long-term prognosis if managed properly during the acute phase and rehabilitation.