Pain Empathy and Its Association with the Clinical Pain in Knee Osteoarthritis Patients

Abstract

Objective: Knee osteoarthritis (KOA) is a painful chronic disorder. Evidence has shown that a history of chronic pain plays an important role in shaping empathy. Empathy, a valuable indicator of social functioning that refers to an individual's ability to share the experiences of others, however, has been overlooked in KOA patients. This study aimed to investigate empathy and its association with clinical pain in KOA patients.

Methods: KOA patients (n=47) and healthy controls (HCs, n=44) completed two empathy-for-pain tasks: a pain judgment task in which participants judged whether a person in an image felt pain or not, and a pain rating task in which they estimated pain intensity for themselves and others. The Interpersonal Reactivity Index was used to measure participants' trait empathy, and clinical severity and psychological factors were assessed using relevant instruments.

Results: Compared to HCs, KOA patients showed higher accuracy when judging pain and non-pain images and reported overall higher pain intensity when rating for themselves and others. KOA patients also showed greater personal distress than HCs in terms of their self-reported empathy. Moreover, pain catastrophizing particularly mediated the relationship between pain severity and pain ratings for others, and depression, anxiety, and pain catastrophizing all mediated the association between pain severity and empathy-induced personal distress.

Conclusion: These findings suggest that patients with KOA have increased empathy, demonstrated by elevated sensitivity to pain-related scenes and intense emotional responses.

Keywords: emotion; empathy; knee osteoarthritis; pain; pain catastrophizing.

Figure 1

Sample stimuli, task designs, and procedures. Stimuli used in the current study are digital photographs showing another person’s left or right body part (eg, hand/foot) in painful or neutral situations. Four representative examples of stimuli (painful/left, painful/right, neutral/left, neutral/right) are displayed in four task sample trials. In Experiment 1, participants indicated whether the person in the image was suffering pain or not in the pain judgment session and whether the image depicted the left or right side of the body part in the laterality judgment session. In Experiment 2, participants reported the pain intensity of the depicted painful image for themselves and others respectively.

Figure 2

(A) Judgment accuracy for conditions of pain (painful or not) and body laterality (left or right) judgments between KOA and HC groups in the judgment task. p values indicate simple t-test results following the significant interaction. Error bars represent standard deviations. (B) Medians of pain rating for conditions of rating for self and others between KOA and HC groups in the rating task. KOA > HC indicates the main effect of the group. Self > Other indicates the main effect of the condition. Error bars represent interquartile ranges.

Figure 3

Positive correlations between pain judgment accuracy and pain ratings in healthy controls (A and B). No correlations in knee osteoarthritis patients (C and D).

Figure 4

(A) The mediating role of pain catastrophizing on the effect of pain severity (WOMAC) on empathy for pain (pain ratings for others). (B–D) The mediating roles of depression, anxiety, and pain catastrophizing on the effect of pain severity (WOMAC) on empathy (IRI - personal distress). ***p < 0.001; **p < 0.01; *p < 0.05; ^#p = 0.06, which indicates a marginal significance. Values in [] represent bootstrapping results with 95% confidence intervals for the lower and upper limits.