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- Issue 10
- ILLUSORY RESIZING OF THE PAINFUL KNEE…
ILLUSORY RESIZING OF THE PAINFUL KNEE IS ANALGESIC IN SYMPTOMATIC KNEE OSTEOARTHRITIS
BACKGROUND & OBJECTIVE
Previous research has shown that visuo-tactile illusions have an analgesic effect on hand osteoarthritis (OA). This study sought to determine whether such illusions can have an analgesic effect on knee OA, and whether sustained or repeated illusions might offer cumulative benefit.
Knee pain intensity (0-100 numerical rating scale; 0 = no pain at all and 100 = worst pain imaginable) was assessed before and after 8 different illusory conditions:
- Two "visual-only" illusions: a headcam showed the knee getting larger or smaller.
- Two "tactile-only" illusions: the skin on the knee was either stretched or compressed.
- Two "congruent visuotactile" illusions: the visual and tactile stimuli were applied at the same time and the same direction (visual stretch and tactile traction; visual shrink and tactile compression)
- Two "incongruent visuotactile" illusions: the visual and tactile stimuli were applied at the same time and opposite directions (visual stretch, but tactile compression; visual shrink, but tactile traction)
After determining which illusion was most analgesic, it was sustained for a longer time period, and repeated over additional sessions, to determine whether it provided cumulative benefit.
Both congruent visuotactile illusions caused a 25% reduction in pain. Only one of the two incongruent visuotactile illusions reduced pain. The tactile-only and visual-only illusions did not reduce pain. When the congruent visuotactile illusion was sustained, analgesia was prolonged but