When Shady was pregnant, I spent a lot of time making sure her diet was properly balanced. Obviously, I wanted her and the baby to be as healthy as possible. I researched proper diets, exercise levels, vaccine schedules; any and everything on pregnant mares. She got as much hay as she wanted, a well balanced grain diet, supplements, an in and out stall with a large paddock attached, and lots of attention of course. I had ridden her lightly up until she was 8 months pregnant, then we resorted to going for long handwalks. My vet was at the barn frequently checking on her and she was very pleased with her progression.

The average horse gestation is 11 months. Shady decided to go one full year and two weeks. The birth was not an easy one, as Indy’s legs just seemed to go on for days. When he finally stood to nurse, he was 10.3 hands high at birth. I still don’t understand how he fit in Shady!

Shady & Indy (28)
Legs for days!

As adorable as this giant bundle of legs was, my immediate concern was OCD. Clearly, he’s going to be a big boy, and he’s going to grow fast. Despite all my efforts at prevention, I began to notice swelling on his left hock when he was about 5 months old. X-rays confirmed it; my boy has OCD.

As I began talking with people about it, I realized there are many that haven’t heard of OCD, or don’t have a full understanding of what it is. As I am going through it personally, I want to use my experience to educate others.

What is OCD?

OCD, or osteochondrosis dissecans, is a common term heard among horse owners, especially those dealing with young horses. OCD and OC (osteochondrosis) are often used interchangeably, though both fall under a more general term of Developmental Orthopedic Disease (DOD). For the purposes of this article, let’s focus on OCD, the more advanced form of OC.

OCD is a very common developmental disease, affecting the cartilage and bone within the joints of the horse. It occurs in roughly 5%-25% of horses and can occur in any breed; however it is most common in large, fast growing breeds. In general terms, it is a growth disturbance. As the horse grows, the cartilage fails to mature properly. OCD is technically when that cartilage then forms cracks and fissures. That cartilage and bone is then loose in the joint, often referred to as “bone chips” or “joint mice.”

OCD occurs when the cartilage in the joint doesn’t form normally during periods of growth. The cartilage, and the bone underneath it, becomes irregular in thickness and thereby weaker than normal joints. These pieces can then remain partially attached to the bone or they can break off and be free-floating. These abnormal pieces, whether attached or not, can cause pain, inflammation, lameness, and eventually may lead to arthritis.

This video is an excellent description of growth and how disruption leads to OCD.  This is from the discussion of Indy’s x-rays with my surgeon:

The most common sign of OCD is swelling in the joint. Lameness is often not observed until the horse begins training. OCD can form in any joint in the body, but the most common are the hock, stifle, and fetlock.

Indy’s hocks; you can see the swelling on the left hock.

There are numerous potential causes of OCD including:

  • Genetics – horses may be partially genetically predisposed to OCD.
  • Rapid growth – Horses that grow too big and too fast are at an increased risk for developing OCD.
  • Nutrition – An imbalance of minerals in the diet has been linked to increased risk of OCD. In particular, diets low in copper increase the risk. However, one cannot just simply increase the daily Copper intake. Numerous minerals, including Iron, Zinc, and Manganese, must also balance, as they interact with the Copper in the diet.
  • Trauma – Injury or high stress on the joints can add to the irregularity of the cartilage and lead to a breakage of the bone fragment.
  • Hormones – Hormonal imbalances, in particular an imbalance of Insulin and Thyroid hormones, can increase the risk as this imbalance affects cartilage development.
  • Blood flow – One study I read mentioned that there is a possible link between temporary loss of blood flow to the joint and OCD formation. This could relate to smaller mares having larger foals cramped in their womb.  Given Indy’s size, this theory fascinated me, and I will be looking into it more.

Now that we have it, what do we do?

Weaning time, typically about 4-6 months, is considered “the age of no return.” Basically, if they have OCD lesions, they are unlikely to form additional lesions. Indy was X-rayed at 6 months old, where we definitively diagnosed the OC in his left hock joint. The piece had not yet broken off yet.

I began discussing options with multiple vets. There are some OCD lesions that can resolve on their own. Of course, OCD lesions in the hock do not resolve on their own. The best option for Indy is to have surgery to remove the pieces.

Arthroscopic surgery is the common approach. It is minimally invasive; two small holes are placed through the skin and down into the joint. A tiny camera is then placed through one hole, and a small tool in the other. The camera then allows the surgeon to guide the tools to remove pieces and clean up the area. Humans frequently have the same surgery to clean up damage to their joints as well.

Left Hock
The larger circled area is the piece that has broken off.  You can see where it would have fit perfectly with the normal bone.  The smaller circle is a loose piece that has not yet broken off.  Both pieces will be removed and the area cleaned up.

Indy has two small pieces in his left hock and one small piece in his right hock.  Both hocks will be done at the same time.  The surgery should take less than 2 hours.  Prognosis is extremely good; the overwhelming majority of horses return to full function and can reach their maximum potential. Indy will need 3 weeks of stall rest, followed by a month turnout in a small paddock. He can then return to normal.

While I absolutely hate to put Indy through this ordeal, this is the best time for him.   I don’t want him to do any further damage to his joints, I don’t want him in any pain, and at his age, he will heal very fast.  The bone will continue to remodel for at least another year, healing the area.  The initial x-rays were done in November; we made the decision to wait until wintertime, when the weather is lousy and the horses aren’t getting as much exercise in their paddocks as normal. He will recover just in time for early spring, and can race around his paddock happily.


18 thoughts on “OCD”

  1. So sorry that you and your little (big) boy have to go through this, but what a well written, informative article. Thank you for taking the time to write and share this.

    Liked by 1 person

  2. Thinking positive thoughts, although all cases are different I know many people in the racing business that will gamble on a well breed baby at a sale with these issues and do what your doing and make out well. Knowing you’ll give him the best

    Liked by 1 person

  3. Very good article. I myself have had 2 Percheron foals with OCD in the stifles for both of them. I lost both of them due to the progression of it so quickly. The first one I knew nothing about ocd the 2nd one I had surgery done on and 2 weeks after the surgery he wasn’t able to get up on his own.


  4. Don’t forget that there can be environmental causes as well. A study of Standardbreds found that those born and raised on clay/hard ground were more likely to develop lesions.

    Liked by 1 person

  5. I found this SUPER fascinating, thanks for the awesome writeup! In your research did you happen to discover if there are any options for older horses that have OCD? For example, a 4 year old off the track who has a chip? Is it the same kind of deal — could be surgical, might not be? You see a lot of horses dismissed because they have OCD and it would be great for people to have a bit more understanding about how this might really affect future performance.

    Liked by 1 person

    1. Hi! Thank you! I enjoy sharing my experiences and helping others learn. Not enjoying the experience itself though!

      I actually heard a story today about a 15 year old horse who had an unknown lameness. He reacted to a hock flexion, but that was it. X-rays found a previously undiscovered OCD lesion. He had the surgery to have it removed, and was fine after that!

      I know there are some that fuse in their own, commonly in the stifle and fetlock. Not the hocks. Is the horse showing lameness? Swelling? It may be worth it to investigate, especially at 4 years old!


      1. Oh, that wasn’t actually a specific example, I was just pulling a common theme out of concerns I see on facebook groups that deal with OTTBs. I work with an organisation that rehomes OTTBs so it’s really good for us to know that OCD is not something that should disqualify a horse from the retraining program, if it’s treatable, of course. 🙂

        Liked by 1 person

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