The simplest measuring device, the verbal rating scale (Figure 6.1A), records on paper or a computer what a patient reports – whether there is ‘no pain’, ‘mild pain’, ‘moderate pain’, or ‘severe pain’.

Figure 6.1 A: A verbal rating scale. The patient is instructed to mark the verbal description that best represents their pain. B: A numerical rating scale. The patient is instructed to mark the numbered vertical line as appropriate. C: A horizontal visual analog scale for pain intensity.

(Reproduced with permission from Kolt & Andersen 2004.)

Numerical rating scale (NRS)

A numerical rating scale (Figure 6.1B) uses a series of numbers (zero to 100, or zero to 10): no pain would equal zero; worst pain possible would equal the highest number on the scale. The patient is asked to apply a numerical value to the pain and this is recorded along with the date.

Using a NRS is a common and fairly accurate method for measuring the intensity of pain, but does not take account of the ‘meaning’ the patient gives to the pain.

Visual analog scale (VAS)

This widely used method (Figure 6.1C) consists of a 10-centimeter line drawn on paper, with marks at each end and at each centimeter. The zero end of the line equals no pain at all; the 10-centimeter end equals the worst pain possible. The patient marks the line at the level of their pain.

The VAS can be used to measure progress by comparing the pain scores over time. The VAS has been found to be accurate when used for anyone over the age of five.

Questionnaires

A variety of questionnaires exist, such as the McGill Pain Questionnaire (Figure 6.2) and the Short-form McGill Pain Questionnaire (Figure 6.3). The shorter version lists a number of words that describe pain (such as throbbing, shooting, stabbing, heavy, sickening, fearful).

Figure 6.2 McGill Pain Questionnaire. The descriptors fall into four major groups: sensory, 1–10; affective, 11–15; evaluative, 16; and miscellaneous, 17–20. The rank value for each descriptor is based on its position in the word set. The sum of the rank values is the pain rating index (PRI). The present pain intensity (PPI) is based on a scale of 0–5.

(Reproduced with permission from Melzack 1975.)

Figure 6.3 The Short-form McGill Pain Questionnaire. Descriptors 1–11 represent the sensory dimension of pain experience and 12–15 represent the affective dimension. Each descriptor is ranked on an intensity scale of 0 = none, 1 = mild, 2 = moderate, 3 = severe. The present pain intensity (PPI) of the standard long-form McGill Pain Questionnaire and the visual analog scale are also included to provide overall pain intensity scores.

(Reproduced with permission from Melzack 1987.)

Use of such questionnaires requires training so that accurate interpretation can be made of the patient’s answers; therefore, apart from acknowledging that they can be very useful, the McGill (and other) questionnaires will not be discussed in this book.

There are a number of ways of obtaining further information, the simplest being to conduct a web search using ‘McGill questionnaire’ as the key words.

Pain drawings

It can be useful for the patient to color the areas of their pain on a simple outline of the human body using a red pencil (Figure 6.4A). The patient should write single-word descriptions of the pain in different areas (e.g., throbbing, aching, etc.), or a simple code can be used, for example: xx = burning pain, !! = stabbing pain, oo = aching, and so on. This record of both the location and the nature of the person’s pain can be compared with similar records at future visits.

Figure 6.4A Outlines of human body onto which the patient sketches patterns of pain.

The shaded or colored areas can be very useful when searching for trigger points, in combination with the body maps provided earlier in this chapter.

A single sheet of paper can easily contain a VAS and a shortened McGill Questionnaire, as well as a series of simple questions such as those illustrated in Figure 6.4B.

Figure 6.4B Pain chart for gathering descriptive terms from the patient, and for sketching pain patterns.

Pain threshold

Applying pressure safely requires sensitivity. We need to be able to sense when tissue tension/resistance is being ‘met’ as we palpate, and when tension is being overcome.

When applying pressure you may ask the patient: ‘Does it hurt?’ or ‘Does it refer?’ To make sense of the answer it is important to have an idea of how much pressure you are using. The term ‘pain threshold’ is used to describe the least amount of pressure needed to produce a report of pain, and/or referred symptoms, when a trigger point is being compressed.

It is important to know how much pressure is required to produce pain, and/or referred symptoms, and whether the amount of pressure being used has changed after treatment, or whether the pain threshold is different the next time the patient comes for treatment. It would not be very helpful to hear: ‘Yes it still hurts’ only because we are pressing much harder!

When testing for trigger point activity, we should be able to apply a moderate amount of force, just enough to cause no more than a sense of pressure (not pain) in normal tissues, and to be always able to apply the same amount of effort whenever we test in this way. We should be able to apply enough pressure to produce the trigger point referral pain, and know that the same pressure, after treatment, no longer causes pain referral.

How can a person learn to apply a particular amount of pressure, and no more? It has been shown that, using simple technology (such as bathroom scales), physical therapy students can be taught to accurately produce specific degrees of pressure on request. Students are tested applying pressure to lumbar muscles. After training, using bathroom scales, the students can usually apply precise amounts of pressure on request (Keating et al 1993).

Algometer

A basic algometer is a hand-held, spring-loaded, rubber-tipped, pressure-measuring device (Figure 6.5A) that offers a means of achieving standardized pressure application.

Figure 6.5 A: Mechanical pressure algometer being used to measure applied pressure. B: A version of an electronic algometer. C: Electronic algometer pressure pad attached to thumb (and to computer). D: Electronic algometer being used to evaluate pressure being applied to upper trapezius trigger point.

Using an algometer, sufficient pressure to produce pain is applied to preselected points, at a precise 90-degree angle to the skin. The measurement is taken when pain is reported. An electronic version of this type of algometer (Figure 6.5B) allows recording of pressures applied; however, these forms of algometer are used independently of actual treatment to obtain feedback from the patient (e.g., to register the pressure being used when pain levels reach tolerance).

A variety of other algometer designs exist, including a sophisticated version that is attached to the thumb or finger with a lead running to an electronic sensor that is itself connected to a computer (Figure 6.5C). This gives very precise readouts of the amount of pressure being applied by the finger or thumb during treatment.

Baldry (1993) suggests that algometers should be used to measure the degree of pressure required to produce symptoms ‘before and after deactivation of a trigger point, because when treatment is successful, the pressure threshold over the trigger point increases’.

If an algometer is not available, and in order to encourage only appropriate amounts of pressure being applied, it may be useful to practice simple palpation exercises.