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). [1]

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. [1]

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. [2]

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. [1]

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Mechanical Lameness

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. [3]

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. [4]

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. [1]

Neurological Lameness

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: [2]

  • Short, choppy strides
  • Buckling over at the fetlock
  • Abnormal posture, such as hunching of their back
  • Stumbling, especially when going