Myofascial pain syndrome is one of the major causes of chronic pain and trigger point injection is often used in clinical situation for treatment of myofascial pain syndrome. Recently, measurement of pressure threshold using pressure algometer was introduced as an useful and reliable mean to detect the trigger point and evaluate the effect of treatment in patients with myofascial pain syndrome.

Authors examined the changes of pressure thresholds over 46 myofascial trigger points among 22 patients before and after trigger point injection therapy with procaine and also tested McGill pain questionnaire, visual analogue scale(VAS), and verbal rating scale(VRS).

Mean pressure thresholds before, immediately after, and three to seven days after trigger point injection were 0.39kg/㎠, 1.75kg/㎠, 2.4kg/㎠, respectively. There was statistically signficant increment of pressure threshold after trigger point injection therapy. VAS and VRS scores showed statistically significant decrement after trigger point injection and there were correlations between changes of VRS and pressure threshold before and after trigger point injection therapy.