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What are Bone Cysts?

Lameness is common in horses, and can come from a variety of causes. Bone cysts are a relatively common disease that affects the joints, usually the stifle, coffin, pastern and elbow joints. A predisposition towards osteochondrosis (OCD) in your horse may also trigger a bone cyst. If your horse is a fast-growing large breed of horse, they may be affected by this at some stage in their lives. The degree that these cysts affects your horse depends on the age and health of your horse, and more importantly, where the cyst is located.

A bone cyst is not filled with fluid but consist of weakly formed bone and cartilage that is circular in outline.  Evaluation of the cyst is important in order to determine the effect on your equine.

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Symptoms of Bone Cysts in Horses

  • Intermittent lameness – it self-heals with rest only to redevelop when returning to exercise
  • The lameness varies and can be either moderate to severe in character
  • Inflammation of the joints (for example the fetlock and the stifle) 
  • Limping or an unusual gait 
  • Reluctance to exercise 
  • Loss of performance 
  • Pain in the joint 

Types  

  • Bone cysts begin when a hole in the cartilage that usually protects the bone is formed; this hole allows joint fluid to seep into the bone causing tissue to erode and over time the cyst grows large and affects your horse considerably
  • Damaged cartilage has poor healing properties and is never the same once damaged 
  • Occurs often in young fast growing horses 6 months to 3 years old
  • It can affect both limbs yet one limb only results in lameness

Causes of Bone Cysts in Horses

  • The cause is still unclear as to why bone cysts form 
  • Generally considered to be weak bone formation beneath the smooth cartilage that covers the joint surface
  • One reason could be caused by trauma to the bone directly under the cartilage 
  • Nutrition
  • Trauma to the bone
  • Genetics may be a cause
  • Overworking younger horses causing bone trauma
  • Copper or calcium deficiency 
  • Phosphorous excess

Diagnosis of Bone Cysts in Horses

Your veterinarian will examine your horse physically to evaluate the lameness and eliminate any other possible causes for the condition. The degree of lameness varies considerably, and that factor will determine the treatment for your house. He will be looking for signs of a build-up of fluid around joints, inflammation, reduced joint flexion and pain.

Radiographs are necessary to reveal the bone cyst as it is hard to detect it otherwise. If your equine specialist finds a bone cyst on one limb they will do a check on the corresponding limb to check that it is not affected as well as often your horse may have developed the cysts on both limbs, even though it is only affecting the one.  Sometimes the x-ray will not show the cyst up in enough detail and a bone scan such as anultrasound may be used to confirm diagnosis. The bone cyst often is identified by its appearance as a black hole in the bone. The bone cyst often causes damage to the cartilage that covers the bones and once damaged, the cartilage is never the same.

Treatment of Bone Cysts in Horses

Treatment can be non-surgical or surgical. Non-surgical therapy requires rest for a few months to see whether it will calm down, combined with medication to take away the inflammation. Your veterinarian may inject the joint with hyaluronic acid or corticosteroid’s but this may not always solve the problem. There are several oral joint supplements, but as they vary in concentration and the source of the product varies, it is advisable to ask the veterinarian on what is best for your horse. It also depends on what joint is involved.

Surgical treatment involves injection into the cyst with corticosteroid’s and surgery often entails arthroscopy which requires keyhole surgery to drill into the cyst from outside the joint. Other such treatments such as joint resurfacing techniques and joint fusion provide extra options but it will depend on the location and accessibility of the damaged site as to whether these options will work. Stem cell therapy is an exciting new application that is showing promise, but is still in the early stages but holds a lot of promise for the future.

Recovery of Bone Cysts in Horses

Recovery for bone cysts varies from horse to horse, depending on the severity, location, and the treatment administered. A large amount of cases responded to rest and returned to full duties once recovered. But this is not always the case and it varies a lot. Often your veterinarian will suggest this method first, before exploring other options. Younger horses seem to recover better to surgery than older horses, this may be due to the fact that younger animals heal quickly. Older animals often have other factors included with bone cysts that affect their recovery, with case studies stating that only one in three older horses returned to work. This is one disease that varies from case to case, but the prognosis is generally good.

Bone Cysts Questions and Advice from Veterinary Professionals

simon
riding pony x thoroughbred
rising 2
Mild condition
0 found helpful
Mild condition

Has Symptoms

Bony Lumps

We brought a 2year old, unbroken, done nothing , he has two bony lumps on his near side hind pastern pretty much in the middle between hoof and fetlock, he is not lame they are not sore to touch, he is just in the paddock not broken in

Health Expert
Dr. Callum Turner, DVM
1722 Recommendations
The lumps may be a bony inflammatory response to an old injury, if Simon isn’t lame or the lumps are not warm or painful I would just monitor them for the time being; kicking himself whilst in the paddock or fighting with another horse may have have caused an injury before. Just keep an eye on the lumps and bring them up with your Veterinarian during the next visit to your yard or stable. Regards Dr Callum Turner DVM

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