Research has shown that the experience of pain is highly subjective: people feel more or less pain, in identical physical situations, as a function of their mood and attention. This flexibility showcases the potential for cognitive manipulations to decrease the pain associated with a variety of pathologies. As an example, the virtual-reality game "Snow World" (in which game in which players shoot snowballs to defeat snowman Frosty and his penguins) reportedly works better than morphine at counteracting the pain of patients in burn units. Other studies have indicated that virtual reality manipulations of the patient's own body can also help ameliorate pain: an experiment conducted by neuroscientist Maria Victoria Sanchez-Vives and her team at the University of Barcelona in Spain showed that heat applied to experimental participants' wrists felt more painful when their virtual arms turned red than when they turned blue or green.
Following on this tradition, a study published PeerJ last month showed that visuotactile illusions can help the pain experienced by patients suffering from knee osteoarthritis.
According to lead author Tasha Stanton, from the University of South Australia, the idea for the study originated from her observation that "people with knee osteoarthritis have an altered perception of their own body. [Their affected knee] often feels too big, and they also have changes to the way that touch and movement information is represented in the brain." She hypothesized that patients may "respond to illusions that change the way their knee looks."