What does it mean to have a sound horse?
The term ‘soundness’ is used by horse owners to describe how a horse moves. For example, a horse is not sound if they are limping or there is a deviation in their gait.
However, soundness refers to much more than just movement. It also encompasses a horse’s overall health and wellness and ability to perform the job they are meant to do.
Horses are considered perfectly sound if they have no health issues and move perfectly without veterinary intervention (i.e. injections or pain control). 
As you can imagine, perfectly sound horses that never require intervention are very rare. A horse may be perfectly sound for only a short period of its life.
However, most horses are serviceably sound or practically sound. These horses can perform their intended job with some maintenance and are pain- or illness-free.
Soundness and Lameness
Soundness in horses is defined as the absence of lameness or illness. A sound horse is capable of performing the work required of it without risking injury.
In terms of gait and movement, a horse that moves abnormally is considered unsound, even if they are not in pain.
This is referred to as mechanical lameness. These horses move through the walk, trot, canter, or gallop abnormally due to some anatomical fault or prior injury. 
Horses can also be neurologically lame. These horses move abnormally due to issues with the central nervous system (the brain and spinal cord) or peripheral nervous system (nerves branching off the spinal cord). Chronic neurological lameness can result both from persisting neurological problems and from weakened muscles, as the nerves cannot properly communicate with the muscles. 
Finally, a horse that moves abnormally due to pain or injury is said to have pain lameness. Pain causes the horse to avoid weight-bearing or motion in the affected area, resulting in abnormal movement. Lameness is most commonly caused by pain. 
Mechanical lameness can be caused by abnormal anatomy present at birth, like a malformed pelvis or club foot.
Affected horses will usually figure out how to move so they can remain comfortable and mobile, but they will likely require frequent veterinary checks to determine if they are experiencing pain in other regions of their body. 
Most mechanical lameness is caused by scar tissue from a previous injury. Scarring forms at the site of tissue damage due to illness or injury.
Scar tissue has a bridge-like structure that re-connects healthy tissue. For example, when a tendon tears, scar tissue joins the two ends of the tendon back together again.
While scar tissue formation is a sign that an injury is healing, its presence can impede natural movement in the affected area. Scarred connective tissue causes abnormal movement because it is thicker than healthy tissue. 
Normally, when a horse moves the tissues stretch, glide and retract to support the motion, but scar tissue is less elastic and cannot move in the same way.
Scar tissue is often not painful, but it can cause compensation in other parts of the horse’s body that may result in pain. If you notice your horse moving abnormally, have your veterinarian examine your horse for signs of pain. 
Neurological lameness can be caused by injury or disease to the horse’s nervous system, including the brain, spinal cord, or the nerves extending off the spinal cord.
These horses may exhibit the following symptoms: 
- Short, choppy strides
- Buckling over at the fetlock
- Abnormal posture, such as hunching of their back
- Stumbling, especially when going up or down small steps
- Abnormal behaviour, such as extreme reactivity or listlessness.
Neurological lameness is not usually associated with pain. Instead, it is characterized by dysfunction in how the nerves communicate with the muscles.
Neurological lameness should not be ignored. Nervous system issues are serious and quick intervention is required. 
Lameness and abnormal movement are most commonly caused by pain.  This may be due to an injury, fracture, degenerative joint disease, inflammation, bruise, infection, skin wound or another source of pain.
Pain-related lameness can present as limping, stiffness, or even an “off” look to the horse as they move. It is categorized as weight-bearing or nonweight-bearing lameness. 
Horses with weight-bearing (supporting leg) lameness will try to reduce the force applied to the affected limb.
Horses with non-weight bearing (swinging leg) lameness will be reluctant to bear any weight on their limb and may swing the leg without touching the ground. 
AAEP Lameness Scale
Lameness is scored on a standardized scale developed by AAEP (American Association of Equine Practitioners). 
Grade 0: Lameness not perceptible under any circumstances
Grade 1: Lameness is difficult to observe and is not consistently apparent, regardless of circumstances (e.g. under saddle, circling, inclines, hard surface, etc.)
Grade 2: Lameness is difficult to observe at a walk or when trotting in a straight line but consistently apparent under certain circumstances (e.g. weight-carrying, circling, inclines, hard surface, etc.)
Grade 3: Lameness is consistently observable at a trot under all circumstances
Grade 4: Lameness is obvious at a walk
Grade 5: Lameness produces minimal weight bearing in motion and/or at rest or a complete inability to move.
Lame horses can be treated with injections or pain medication to improve their mobility. However, if the horse requires maintenance with medications to remain pain-free, they are no longer considered sound.
It is important to understand that an unsound horse may not be in pain, as in the case of mechanical or neurological lameness. However, a horse that is in pain is unsound, regardless of if they are lame or not.
Pain in the Absence of Lameness
Horses are herbivorous prey animals. In the wild, they face predation from several large carnivores including wolves, cougars, and even bears.
Because of their prey animal instincts, they do not like to show signs of pain. If a predator is hunting a herd of animals, it will often opportunistically attack an animal with a defect before a healthy and strong-looking animal. 
Although domesticated horses are generally free from the risk of predation, these evolutionary instincts remain. This means that if your horse is showing signs of pain, they are likely experiencing significant pain. 
Signs of Pain in Horses
Pain does not always present as lameness or abnormal movement. It can also present as: 
- Abnormal behaviour such as bucking or bolting
- Changes in appetite or weight
- Lethargy or looking dull
- A tense expression
- Grinding teeth
- Abnormal sweating
A horse that is in pain but not lame is considered unsound. A veterinary lameness examination is warranted if you think your horse is experiencing pain.
Serviceable soundness is the classical concept referring to horses that is “sound in the wind and eyes and not lame.”  Servicably sound horses can perform their intended job at the desired level with some extra attention or intervention. 
A serviceably sound horse may require maintenance in the form of joint injections or low doses of pain medication to remain pain-free in their job.
The majority of horses are considered serviceably sound. Even horses competing at the highest level usually require some intervention to keep soreness or stiffness at bay.
Interventions to maintain soundness usually include:
- Joint injections such as Hyaluronic Acid, PRP, IRAP, or ProStride
- Low-dose non-steroidal anti-inflammatory medication (NSAIDs) such as Previcox
- Corrective shoeing
- Other consistent veterinary intervention
Conformational soundness refers to whether the horse is built to perform the job they are asked to do. For example, a conformationally sound Western Pleasure horse may not be a conformationally sound jumper.
Most horses can perform in any discipline at a low level. However, horses not conformationally suited to performing in a discipline at a high level are more susceptible to injury. 
Purchasing a Conformationally Sound Horse
When purchasing a horse, the most important thing to ask yourself is, “What do I need this horse to do?” You want to ensure that the horse you are interested in buying is well-suited to the job you will ask it to perform.
Consider the horse’s conformation and determine if they are right for your level and discipline. A Pre-Purchase Exam from your veterinarian can help you with this.
If the horse is not perfectly suited to your discipline, ask yourself if conditioning can counter any faults they have. Training and exercise can reduce the impact of minor conformation issues. For example, a horse with a weak hind end can practice exercises to strengthen the area, making dressage work easier.
Severe Conformation Faults
Although some minor conformation faults can be mitigated with careful conditioning, some conformation faults are more severe. These faults are more likely to result in lameness:
- Back at the knee: The cannon bone angles backwards, causing the knee to lie behind the vertical
- Straight hocks: There is little to no bend to the horse`s hocks; the hind leg is almost completely straight
- Upright pasterns: The pasterns are too vertical with little break at the fetlock
- Roach back: Otherwise known as “kyphosis”, the back humps upwards
Horses with these conformation faults are less likely to remain sound in work, regardless of conditioning.
A horse with conformational issues will experience improper force distribution through their body, leading to strains and sprains, arthritis, or even pressure fractures. 
Horses with conformation faults that impact their performance in a chosen sport are not considered conformationally sound. Because disciplines vary widely in their required conformation, a conformationally sound horse in one discipline may not be conformationally sound in another discipline. 
Soundness refers to the horse’s overall well-being and factors in the presence of disease or chronic conditions. A horse with a chronic condition or disease is not considered sound, even if it is not lame.
Some common conditions that impact the soundness of a horse include but are not limited to:
- Chronic ulcers
- Recurring colic
- Chronic eye ulcers
- Kissing spine
Chronic health conditions impact the way a horse performs their job and lives their life. Although a horse with a chronic condition is not considered sound, you can support their health and well-being with diligent veterinary care and good horsemanship.
Maintaining a Healthy and Sound Horse
While it is difficult to keep your horse perfectly sound throughout their entire life, there are many ways to maintain your horse’s health to keep them as sound as possible.
Preventative Veterinary/Farrier Care
Providing preventative veterinary and farrier care is the first step to a sound, healthy horse. Ensure that your horse receives the following care regularly:
- Veterinary-guided worming protocols
- Yearly vaccinations
- Daily health checks by the caregiver to catch disease quickly
- Routine farrier care
- Routine teeth floating
Providing routine care will keep your horse healthy and sound for as long as possible. It will also help your horse avoid costly preventable health emergencies.
Good facility management is an important component in keeping your horse healthy. Clean, well-ventilated barns help to prevent respiratory issues and reduce the risk of bacterial infections.
- Ensure your barn has appropriate ventilation; the air should not be dusty or stuffy
- Provide your horse with low-dust, high-quality hay
- Ensure your horse has constant access to clean, fresh water
- Muck stalls thoroughly to avoid bacterial infections
Nutrition and Exercise
Maintaining a healthy diet and exercise program can help to keep your horse sound. Ensure your horse is not overweight as carrying excess body weight can contribute to lameness.
Consider your horse’s breed, weight, and current fitness when designing a training regimen. Appropriate exercise helps to support mobility and joint health.
If your horse is overweight, they may need consistent low-intensity exercise to improve conditioning. Consult your veterinarian to determine an appropriate exercise program for your horse if they are unsound.
Nutrition is crucial to maintaining a sound horse. Feed your horse a balanced diet with adequate levels of energy, protein, vitamins and minerals.
Is Your Horse's Diet Missing Anything?
Identify gaps in your horse's nutrition program to optimize their well-being.
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