Bone Odema

When looking at the world of animal athletics, injuries are a big concern. One species that has been researched the most for athletic injuries is the horse. Bone injuries are common in young racing horses. Bone bruising is caused by repetitive trauma to the bone while it is still developing. A common injury in racing horses is Bone Oedema, also known as bone bruising. Bone Oedema is an injury to the subchondral bone, the layer of the bone that abuts cartilage in weight-bearing joints. The blood vessels in this layer get bruised by repetitive trauma to the bone. This injury is primarily reported in thoroughbreds and standardbreds because they train at a high intensity. Bone Oedema is an injury that can affect these two breeds of horses’ overall performance if not prevented in its early stages.
Imagine that you are a new horse trainer that trains standardbred horses for racing. You have obtained some young standard breeds to start training. It is usual for a standardbred horse to begin racing at two years of age and race until it is eight years old. The owner of this horse wants to start training as soon as possible to prepare the horse for its first big race. When a horse is training for racing, the muscle and skeletal system undergo many forces. Racing requires training that is very intense and repetitive. When you start preparing the standardbred horses for competition, you will condition them every other day by jogging the horse one way around the track for 3 to 6 miles. Then you will jog them around the track the other way. The goal of this training is to improve the speed of the horse on the track. When looking at the length of a Standardbred track, it is typically 1 mile long. The race being shorter means that the horse has to move at a high-intensity speed to become faster than the other horses it will be competing against in the race. The average rate of a horse in these races is 25-30 miles per hour. When looking at the animal’s speed, we can see how the body takes on a lot of force when running straight and taking the corners.

Standardbred horse racing
Figure 1. Example of standardbred horses racing

After a few months, you notice that one horse was not performing to the same level as it was a week ago. You begin to notice the horse is starting to limp on its rear leg. When feeling the leg to see the problem, you don’t feel any swelling in the joint, but you notice that the rear fetlock joint is sore. Since you can’t find anything swollen in the joint and nothing feels broken, you decide to call the veterinarian. After the veterinarian examines the horse, he decides to take an x-ray because he knows that the fetlock is a zone that takes a lot of force when racing. These forces can lead to bone bruising in the fetlock joint.  When looking at the x-ray, the vet sees an area of bone lysis that will appear darker on the x-ray and a place of sclerosis, which will appear as a light area in the bone.

Bone odema
Figure 2. An example of an x-ray of Bone Oedema

The veterinarian diagnosed the horse with Bone Oedema due to seeing the presence of bone lysis and sclerosis2. This injury happens because the bone is trying to adapt to forces that are traumatic to the bone. The bone will be weaker in the darker and whiter areas on the x-ray, leading to fractures that could be fatal to the horse if not treated.
Once a diagnosis is determined, the veterinarian can create a treatment plan. The veterinarian decides to start treatment by giving anti-inflammatory medicine like Aspirin to help increase blood supply to the damaged area of the bone3. Then he tells you to reduce physical activity for three to four months. Your veterinarian recommends keeping the horse active, and you can try to take it to horse swimming so it can give the sub-chondral layer of the bone time to heal. As a trainer, you want the best for all the horses you are training. You wonder what you could do differently to prevent this injury from occurring, so you ask your veterinarian what he recommends to avoid this from happening again. He tells you that you should try to take exercise easy when on hard surfaces. It would help if you also tried to exercise your horse on different surfaces, from soft to hard, to allow the bone to adapt. After the bone has fully healed the standardbred horse should be able to return to racing. Bone Oedema is an injury caused by repetitive trauma to the bone causing bone bruising, most often found in standardbred horses. It is an injury to the subchondral bone, the layer of the bone that abuts cartilage in weight-bearing joints. Being aware of signs of this injury and preventing it from occurring is essential for the animal’s wellbeing. If the symptoms become worse, consult a veterinarian for further treatment options. The primary indication of Bone Oedema is that the horse starts to limp on its rear leg and that the rear fetlock joint is sore. Treatment includes Anti-inflammatory medicine and rest. To prevent this injury from occurring, try to vary the surfaces that the horse is training on to help prepare the bone for intense exercise.

  1. Bone Oedema. Equine Vets.  Published August 7, 2019. Accessed March 19, 2021.
  2. Bone-related swelling detected in 44% of horses in study. Published July 20, 2019. Accessed March 19, 2021.
  3. Meggitt J. How to Train a Standardbred Racehorse. Pets on Published November 19, 2020. Accessed March 19, 2021.
  4. Staff KER. Bone bruises in Young equine athletes. Accessed March 19, 2021.

By: Quinton Waits and Peggy Auwerda
The report is a project for ANS313 Exercise Physiology of Animals