Osselets, a Latin word for little bones, is a type of arthritis that’s caused by repeated trauma and overuse.
Its appearance is primarily limited to racehorses due to the amount of stress and strain that’s put onto their fetlock joints during the gallop. They’re similar to windgalls in that they’re cosmetic in appearance after they’ve been healed, and won’t affect a horse’s future soundness.
Osselets are considered cosmetic in nature, but their appearance can be off-putting to a potential buyer. However, the fact that the horse that’s been retired from a speed career, and is unlikely to be put to use for that type of work ever again, means the horse has a positive future in terms of staying sound and useful.
Read on to learn more about osselets in horses, their effect on a horse’s physical well-being, and what you can expect from owning a horse with the condition.
RELATED: Windgalls (aka Windpuffs) in Horses: Symptoms, Treatment, & More
As always, the information in this article is for informational purposes only and should not be considered medical advice for your horse. You should always consult with your vet when treating your horse.
What is an Osselet?
The brief description of osselets in horses is that it’s a type of arthritis located in the fetlock and caused by trauma to the joint. In this instance, the use of the word trauma refers to the strain and impact that the fetlock endures during a galloping stride.
The fetlock joint undergoes repetitive strain as the horse’s leg moves through its cycle. Internally, the top of the fetlock joint slams into the bottom of the cannon bone as the horse’s hoof hits the ground and the impact goes up the leg.
The bone of the fetlock joint responds to this trauma by forming a bony callous known as a green osselet. A horse with a green osselet will exhibit signs of soreness, have a short, choppy gait, and the joint will be warm or hot to the touch. When these conditions appear, the horse needs to be put on stall rest and provided with care and treatment to encourage the healing process to finish with the least amount of discomfort.
How Osselets Form
Have you ever noticed how a racehorse’s fetlocks almost stretch parallel to the ground as they race? This is due to an action known as dorsiflexion, and it’s especially apparent in horses with long patterns.
Because racehorses are always engaged in work at speed, either during training or competition, they’re most likely to develop osselets. Other speed activities with horses are unlikely to result in the formation of osselets because the horse isn’t running flat out for periods of time and isn’t undergoing extreme flexion of the fetlock.
The repetitive action of the fetlock during dorsiflexion causes micro tears in the joint capsule of the fetlock. Over time, the bone forms a lump on the fetlock that hardens over time and creates a permanent ossification. A fresh osselet is known as a green osselet, and the horse will demonstrate soreness during the formation of the callous.
Presentation of Osselets After They Form
Osselets appear as swelling on the front of the fetlock, and are most commonly found on the front legs. You can easily see osselets because they give the fetlock joint an inflamed appearance.
An osselet is hard to the touch, cold, and the horse is unlikely to flinch when you touch the bump. You’re more likely to get a lifted leg from the conditioned response of picking out a horse’s hooves than a reaction to a fully-formed osselet.
Treatment for Osselets
A horse should be pulled from the activity after an osselet starts to appear. The sooner you can get on top of the condition, the better.
The primary treatment for the appearance of osselets is stall rest, the application of cold packs, and anti-inflammatories. A vet may use a corticosteroid injection into the joint to reduce inflammation and help the horse’s body heal itself more effectively.
After an osselet has formed and turned cold, no further treatment is required. It has become part of the horse’s bony structure, and is located in an area of the fetlock that has no other function. That is, a horse’s flexor tendons are located to the side and rear of the leg, and don’t travel over the front of the fetlock joint. An osselet won’t interfere with the normal function of the horse’s leg, and will not require ongoing maintenance.
Quality of Life Outlook for a Horse With Osselets
Osselets in horses aren’t necessarily a career-ending injury, even though they look like the horse is permanently lame or is likely to become lame again in the future. A horse may have its racing career ended due to the osselets, but that doesn’t mean the horse can never be used again.
Once the osselets are healed, the horse can go on to a second career doing everything from eventing to trail riding without issues. They’re a cosmetic issue only, and shouldn’t deter you from making the purchase of a horse that has the talent you’re seeking for your discipline.
Osselets are not an indicator of a predisposition to arthritis as their cause is mechanical in nature. Racing puts a lot of strain on a horse’s joints, and sometimes a horse’s body has a mild, degenerative response to the strain. You can expect a horse with osselets to go on to have a great future and experience their full potential in whatever discipline you prefer.
Osselets, Windpuffs, and Windgalls: What Are They?
Osselets and windpuffs/windgalls are two different conditions that occur in the fetlock joint. Osselets are a bony condition, while windgalls or windpuffs are a soft tissue condition. It’s possible for a horse to have both windpuffs and osselets at the same time, or individually. These are signs that the horse was used for strenuous work, but received proper care to help it heal and recover from the initial injury period.
A horse with one or both of these conditions will not exhibit signs of lameness. They’re fully capable of unaffected, natural movement, and the osselets won’t affect joint flexion, much less flare up after an activity.
Should You Buy a Horse With Osselets?
You can buy a horse with osselets, provided a lameness exam has shown that the horse is otherwise sound. Once the initial insult heals, the horse remains sound, and the condition is considered “cold.” That is, the bumps will never become active again in the horse’s life, and it can perform in any discipline without restriction.
The external appearance of osselets points to the horse’s previous career as a racehorse and acts as a kind of visual history as to what your horse once did.
If you’re considering a horse with osselets, make sure to have a full lameness exam performed by a veterinarian. Osselets, even when accompanied by windgalls, are not an issue that affects a horse’s ability to perform. You want to make sure there are no other bony changes in the joint and that the joint is free from bone chips or fragments. In the event the vet gives a clean bill of health and finds no issue with the osselets, you can feel confident about purchasing the horse.
Horses that have been raced are most likely to have osselets. That means osselets are most commonly seen in off-track thoroughbreds, but they can form on horses that have been used for speed events, although this is much less common.
A “cold” osselet is a cosmetic issue, and doesn’t affect a horse’s quality of life or ability to perform in a career that’s less strenuous.
Many talented horses retire from their racing career with osselets and go on to have a long, fruitful life in a different discipline. A horse with osselets can be used for dressage, jumping, eventing, and just about any riding activity. Buyers may shy away from a horse with osselets, but the fact is, a horse can be a brilliant performer and never go lame, even with osselets and/or windpuffs.
It’s a wise move to get a pre-purchase exam done on a horse with osselets to make sure they’ve solidified and cold. You want to make sure the horse doesn’t have other conditions that can affect its soundness. That way, you can feel good about your purchase and enjoy the talents the horse has to offer.