It is evident that muscle pain deriving from any type of lesion can refer pain to other deep somatic tissues, yet not just locally. The convergence theory as depicted from animal experimental study of Mense 1994 explains the pain referral sequence. Central sensitization to adjacent spinal segments is present due to nociceptive input from skeletal muscle and myotomes outside the lesion.
Specifically, the refer pain is evident due to synaptic connections peripherally from noxious stimulus. After injecting bradykinin outside the receptive field, substance P (SP) and calcitonin gene-related peptide (CGRP) were released from nociceptive afferent fibers leading to unmasking of unsuccessful connections in the dorsal horn (Mense, 1994).
The convergence theory is portrayed in the Srbely et. al 2010 double-blind randomized controlled study. The study shows that stimulation with the dry needling technique can induce segmental anti- nociceptive effects. The right supraspinatus trigger point (nerve innervation of C4, C5) was needled on the test subjects. The control group received sham intramuscular dry needle puncture. Pain pressure threshold data were gathered from right infraspinatus (C5,6) and right gluteus medius (L4,5, S1) trigger points.
In conclusion, there was direct measure of the segmental anti-nociceptive effects acting at the infraspinatus trigger point because the supraspinatus and infraspinatus trigger points are neurologically linked at C5. Both studies show that the convergence theory exists, yet the antinociceptive effects from dry needling can be present by modulating segmental mechanisms.
1. Mense S. Referral of Muscle Pain. APS Journal 3(1): 1-9, 1994.
2. Srbely J., Dickey J. , Lee D. and Lowerison M. DRY NEEDLE STIMULATION OF MYOFASCIAL TRIGGER POINTS EVOKES SEGMENTAL ANTI-NOCICEPTIVE EFFECTS. Journal of Rehabilitation Medicine, 2010; 42: 463–468.