Ouch!

Pain in humans is easy enough to detect - they'll tell you about it. But how can it be spotted in horses? Liz Richardson MRCVS demystifies pain physiology and recognition

- 

THERE is more to pain than you may realise. Pain can be defined as an unpleasant sensory and emotional experience, associated with actual or potential tissue damage.

This importantly emphasises that pain is not just about a physical sensation, but also about how it makes us feel emotionally, and that it is a very personal experience. The same is true for our horses too.

We all appreciate the emotional impact on a horse when they are in pain.

PAIN PHYSIOLOGY

WHEN understanding how to recognise, assess and treat pain, it is helpful to understand the physiology behind it (that is, the biological processes that occur to cause pain). Pain physiology is complex.

To protect an animal from tissue damage, signals must be produced by the nervous system and this is achieved via the pain pathway. This involves a detection of a potentially harmful stimulus (such as heat, cold, pressure or burns) by pain receptors. These are converted to electrical signals and transmitted to the brain via nerves and the spinal cord. The brain is where pain is perceived and where physiological and behavioural responses are initiated.

Physiological pain (pain of short duration, where minimal or no tissue injury occurs) is a normal response to painful stimuli and serves to protect and maintain integrity of the body. Short-lived pain causes a pre-programmed reaction to minimise further harm – an example in humans would be removing your hand from a hot surface.

In contrast, pathological pain (when pain serves no protective function) usually results from actual physical injury, but can be experienced in various ways, including:

• without a painful stimulus – for example, a sudden pain in your foot

• in response to a normally non-painful stimulus, such as applying gentle pressure to a bruise