Simple Descriptive, Numerical Rating and Visual Analogue Scales are unidimensional and universal instruments of pain measurement, as they evaluate exclusively the intensity of pain and are understood in any language or culture, respectively.
These scales have been developed to assess self-report pain in man, and had to be adapted for using in veterinary medicine, because pain assessment in animals depends on an observer. In veterinary medicine, the value "0“, indicating absolute absence of pain is always arbitrary, as it is not possible to ensure that one animal is completely free of pain.
The Simple Descriptive Scale exhibits degrees of pain intensity (no pain, mild pain, moderate pain and severe pain). The Numerical Rating Scale is a numerical value from 0 to 10, where "0" represents no pain and "10" the worst possible pain. The Visual Analogue Scale is a straight line with 100 mm in length, anchored by the words "no pain" and "worst possible pain".
Simple Descriptive Scale
| 0 | No pain |
| 1 | Mild pain |
| 2 | Moderate pain |
| 3 | Severe pain |
Numerical Rating Scale
| 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
| No pain Worst possible pain | ||||||||||