D8 Pain assessment (algometry)

Topic

Pain assessment combines two types of instruments: validated self-report scales and pressure algometry.

The first type consists of validated self-report scales: the visual analog scale, where the individual marks pain intensity on a continuous line; the numerical scale, where the individual assigns a number to that same intensity; and the neuropathic pain questionnaire, which investigates whether the pain exhibits neuropathic characteristics in addition to mechanical ones. These self-report scales quantify pain intensity and its spatial distribution—that is, the areas of the body where the individual perceives it.

The second instrument is pressure algometry: using a pressure algometer, increasing and controlled pressure is applied to the tissue until the individual reports that the pressure has become painful; this exact point represents the pressure pain threshold. Unlike self-report scales, the pressure pain threshold does not rely solely on the individual's account but is based on a pressure level actually measured at the moment pain arises.

By combining self-report scales with the pressure pain threshold, pain assessment operationalizes musculoskeletal pain: it measures mechanical overload on the tissues—specifically, the amount of elevated tissue pressure a tissue can withstand before that pressure crosses the pressure pain threshold and manifests as musculoskeletal pain.

In addition to mechanical tissue overload, pain assessment measures motor control inhibition secondary to musculoskeletal pain: when musculoskeletal pain occurs, the body responds by simultaneously activating opposing muscles acting on the painful area—a protective co-activation—and this co-activation serves as a physical indicator of the extent to which musculoskeletal pain is inhibiting normal motor control. Of all the data gathered during pain assessment, the pressure pain threshold is the only objective physical measure of musculoskeletal pain available in a clinical setting: while self-report scales depend on what the individual chooses to disclose, the pressure pain threshold is determined by applying actual pressure and measuring the precise point at which that pressure turns into musculoskeletal pain.

ID:13