A visual analog scale (VAS) is a tool doctors use to pinpoint the extent of pain. Doctors have patients look at a scale from zero (no pain) to 100 (the worst pain) and point to the place that best describes what they feel.

VAS seems to capture differences between patients and conditions. It's a popular way for doctors to learn the intensity of pain. VAS can help doctors suggest the right treatment. If the pain is very minor, for example, it's unlikely that surgery is needed. After treatment, VAS can help doctors gauge whether pain has been reduced. This gives information about the success of the treatment.