What are Subchondral Cystic Lesions?
A subchondral cystic lesion in a horse can be found in multiple places and is one of a number of types of conditions which fall under the umbrella of developmental orthopedic diseases (DOD). Subchondral cystic lesions are considered developmental orthopedic diseases because they generally are found in young growing animals and the most common location in which they are found is in the stifle joint (the knee joint) of the horse inside the lower portion of the femur. They can be serious causes of lameness which can have lifelong implications for the athleticism of your equine.
Subchondral cystic lesions, also known as bone cysts, are abnormalities of the bones or joints that may or not cause lameness and these cystic lesions can occur in multiple places in the body of the horse. These cysts are found just under the cartilage in the joint.
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Symptoms of Subchondral Cystic Lesions in Horses
Symptoms of subchondral cystic lesions can be mild to severe and can be of an acute onset. The symptoms you will likely notice are:
- Lameness may be acute or hardly noticed unless the horse is working at specific increased speeds or when involved in specific activities - intermittent, especially in older horses but can be noted in horses of any age
- Lameness will be worse when horse is working or exercising and will ease or improve when the equine is at rest
- Swelling can sometimes be noted in the joint area in some horses but frequently there is no noticeable swelling
The types of subchondral cystic lesions in horses refers to the location of their development and are primarily those found listed below:
- Fetlocks and carpus
These cystic lesions form just under the cartilage in the joint, can be located basically on any joint and are generally unilateral but can be bilateral in the same joint with the above mentioned joint locations being the most commonly found in horses.
Causes of Subchondral Cystic Lesions in Horses
While subchondral cysts or bone cysts are referred to as “cysts” they are not cysts per se as a “cyst” is defined as having an epithelial lining and being fluid-filled but bone cysts do not have the special epithelial lining. Accordingly, they are sometimes defined as “solitary bone lesions”. Here are some of the suspected causes of these cystic lesions:
- Osteochondrosis - abnormal development of cartilage
- Developmental failure of ossification (development of bone tissue)
- Trauma to subchondral bone
- Inflammation activity inside the cyst itself is responsible for enlargement of the cyst and the associated bone pain
It is important to note that these cysts may be present long before they become symptomatic in your equine and, when conditions are right, they show up as lameness. The duration of the cyst can cause problems with future development of the tissue and potentially the future athleticism of the horse. This will come under consideration when the treatment plan is developed.
Diagnosis of Subchondral Cystic Lesions in Horses
As noted above, the subchondral cystic lesion can form on any bone or joint in the skeletal body of the horse. Some of these cystic lesions will present with symptoms while others will not. Some will allow the equine to appear normal in some motions but will display some degree of lameness in other activities especially those requiring increased speeds. Your vet will need to do a thorough physical examination as well as lameness evaluation on your horse.
What your vet is looking for in the lameness evaluation will be is lameness associated with a shorter stride. Historically, these developmental cystic lesions will show up, sometimes with symptoms and sometimes without symptoms, in the younger horse at the time it begins training or exercise regimens increase. Radiography is generally the imaging technique used to diagnose these lesions. Location, size and general appearance of the lesion will help your veterinary professional to determine the diagnosis and what needs to be treated. What is found in the radiographic imaging will determine the treatment.
Treatment of Subchondral Cystic Lesions in Horses
After your vet has evaluated your equine and obtained the radiographic imaging of the suspected area, he will need to ascertain the future plans the owner has for the horse, (racing, show, work performance, pleasure). Once he has received this feedback from you, the owner, he will then put all of the diagnostic and expectation pieces together to form an appropriate treatment regimen which he believes should be initiated. That treatment plan will likely include a period of stall rest, perhaps intra-articular injections of anti-inflammatory medications, oral supplements, dietary changes and exercise recommendations, or any combination of these treatment tools.
Depending on the size, location and duration of the cystic lesion, a surgical option can also be recommended to remove tissue or debridement of the joint if loose pieces are present in those areas, usually utilizing an arthroscopic technique. Removal of the cystic lesion is usually the best course of action, especially if the horse is planned to be offered for sale as the presence of a subchondral cystic lesion will likely decrease its value upon sale. Removal of the cystic lesion will also be advantageous if the horse is to be raced or shown to reduce the possibility of lameness showing up unexpectedly and to reduce the opportunity for the lesion to cause permanent damage which would limit the future athletic abilities of the horse.
Recovery of Subchondral Cystic Lesions in Horses
Depending on the location, size and age of the subchondral cystic lesion, the prognosis for the afflicted horse is good for returning to its previous level of activity in time. If, however, the lesion was present long enough to cause damage to the surrounding tissue and bone, there could be a permanent disability or limitation to the future activities of your equine. Expect that there will be dietary changes, recommendations for rest and exercise, perhaps some oral supplements and long-term anti inflammatory medications included in the recovery regimen. Most of the surgical options would likely increase the opportunity for a better outcome and future for your equine.