Pain was found to improve with scores on the pain catastrophizing scale but not with widespread pain in patients with osteoarthritis (OA) after unilateral total knee replacement (TKR) surgery, according to study results published in Arthritis Care & Research.
Pain catastrophizing and widespread pain have been shown to affect play outcomes after TKR. In the Study of Total Knee Responses, a multicenter prospective cohort trial, 176 patients (mean age, 66.1 years; 63.6% women) with severe OA who were scheduled to undergo TKR between September 2012 and April 2014 were enrolled. Participants had a median Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain score of 40 at baseline. Participants were assessed during the 6 weeks preceding surgery (baseline) and 12 months postoperatively, using the Pain Catastrophizing Scale (PCS), WOMAC pain, and body pain diagrams to evaluate the presence of widespread pain.
Patients were categorized according to baseline level of pain catastrophizing (ie, score <16 or ≥16) and according to the presence of widespread pain (regions with pain: 0, 1-2, ≥3). Participants had mild (44.3%), moderate (51.7%), or severe (4.0%) pain, as indicated by WOMAC pain scores. The baseline mean PCS score was 11.4±10.2, with 131 (74%) and 45 (26%) patients in the low and high pain catastrophizing groups, respectively. There were 42 (24%), 84 (48%), and 50 (28%) individuals with 0, 1 to 2, and ≥3 pain sites, respectively. Changes from baseline to follow-up were assessed and reported in terms of group movements and correlations with WOMAC pain scores.
After 12 months, the mean PCS score decreased to 5.8, with 153 (87%) and 23 (13%) patients in the low and high pain catastrophizing categories, respectively. The distribution of patients by number of pain sites was comparable 12 months after vs before surgery, with 34 (19%), 93 (53%), and 49 (28%) individuals reporting 0, 1 to 2, and ≥3 painful regions. A total of 10 (8%) and 32 (71%) participants had worsened and improved pain catastrophizing, respectively, 12 months after surgery compared with baseline. A total of 73 (41%) participants switched between no/low and high number of pain sites, with 45% improving and 55% worsening from baseline to follow-up.
There was a positive correlation between changes in WOMAC pain scores and changes in levels of pain catastrophizing (r=0.31; P <.001), but not with presence/absence of widespread pain (r=−0.004).
Study limitations include a high noncompletion rate with higher baseline WOMAC pain and catastrophizing scores in excluded participants, a lack of assessment of new comorbidities/injuries, and small sample sizes in the “worst” pain catastrophizing and widespread pain groups.
“The findings urge caution in interpreting PCS and [widespread pain] as trait measures in musculoskeletal research,” noted the study authors.
Lape EC, Selzer F, Collins JE, Losina E, Katz JN. Stability of measures of pain catastrophizing and widespread pain following total knee replacement (TKR) [published online June 7, 2019]. Arthritis Care Res (Hoboken). doi:10.1002/acr.24000