One in five patients experience chronic pain 12 months following total knee arthroplasty (TKA). This longitudinal study used a person-centred approach to identify subgroups of patients with distinct chronic pain profiles following TKA and identified preoperative characteristics associated with these profiles.
On the day before surgery, 202 patients completed questionnaires that assessed pain, interference with functioning, fatigue, anxiety, depression and illness perceptions. Average and worst pain were assessed prior to surgery, on postoperative day 4, at 6 week and at 3 and 12 months following surgery. Using growth mixture modelling, two subgroups with distinct average and worst pain profiles were identified.
Patients in the "lower average" and "lower worst" pain classes had moderate preoperative pain scores that decreased over the remaining 9 months following TKA. Patients in the "higher average" and "higher worst" pain classes had relatively higher preoperative pain scores that increased during the first three months and then decreased slightly over the remaining 9 months. Patients in the higher pain classes had higher interference with function scores; used opioids prior to surgery more often, were more likely to receive a continuous nerve block and ketamine; had higher preoperative fatigue severity and interference scores; and had worse perceptions of illness than patients in the lower pain classes.
The present study provides a novel and original analysis of pain profiles following total knee arthroplasty that may contribute to our understanding of the transition from acute to chronic pain. Our results may be used to identify patients at higher risk for poorer outcomes based on preoperative risk factors.
These risk factors may be used to identify subgroups of patients at higher risk for more severe pain after TKA. Future studies should test whether modifying these risk factors can improve patients' outcomes after TKA.