The effect of knee resizing illusions on pain and swelling in symptomatic knee osteoarthritis: a case report

Abstract

Introduction: Resizing illusions that manipulate perceived body size are analgesic in some chronic pain conditions. Little is known whether such illusions may also alter other physiological features, such as swelling. Objectives: To determine the effects of a knee resizing illusion on knee pain and swelling in symptomatic osteoarthritis. Methods: This case study was extracted from a larger study evaluating the analgesic effects of resizing illusions in people with knee osteoarthritis. A mediated reality system (alters real-time video) was used to provide resizing “stretch” and “shrink” illusions of the knee. Knee pain intensity (0–100 numerical rating scale) was measured before and after illusion and after sustained (3 minutes) and repeated (n = 10) illusions. In this case study, knee swelling (leg circumference below, at, and above the knee) was also measured. Results: The 55-year-old male participant reported a long history of episodic knee pain and swelling that was subsequently diagnosed as severe osteoarthritis in 2013. In the first testing session, the participant experienced an increase in pain with the shrink illusion and a decrease in pain with stretch illusion. A noticeable increase in knee swelling was also observed. Thus, in sessions 2/3, swelling was also assessed. The stretch illusion decreased pain to the largest extent, but resulted in increased knee swelling. Repeated and sustained stretch illusions had cumulative analgesic effects but resulted in cumulative increases in swelling. While the shrink illusion increased pain, sustained (∼10 minutes) visual minification of the entire knee and leg reduced both pain and swelling. Conclusion: Our case report suggests that both pain and swelling may be modifiable by altering body-relevant sensory input in symptomatic knee osteoarthritis.

“But it feels swollen!”: the frequency and clinical characteristics of people with knee osteoarthritis who report subjective knee swelling in the absence of objective swelling

“…Past work in therapeutic targeting of body perception has shown that visuotactile illusions applied using mediated reality can alter the perceived size of the knee in people with knee OA and that such perceptual shifts are analgesic. 49 Intriguingly, these illusions can also alter objective knee swelling in some cases, 24 making them an interesting method to explore whether the phenotypes identified here might have differing clinical responses to brain-targeted treatment. Furthermore, the group reporting only subjective feelings of swelling also had impaired tactile acuity, raising the possibility that treatment targeting impaired sensorimotor representation (such as touch discrimination training and implicit motor imagery training) may be most relevant in this group.…”

Comparison of Short-Term Efficacy of Total Knee Arthroplasty Versus Arthroscopy in Chinese Patients with Knee Osteoarthritis

“…Knee osteoarthritis is a condition based on degenerative pathological changes [1,2], it is more common in middle-aged and elderly people, and its symptoms are mostly red and swollen pain in the knee, pain in going up and down stairs, and sore knee discomfort when sitting and standing [3]. There will also be patients with swelling, popping, effusion, etc [4]. If not treated in time, it will cause joint deformities or disability [5].…”