Background/Purpose:

Up to 47% of individuals may not have clinically significant improvement following joint replacement surgery. Evidence also suggests that women are less likely to benefit from TKR surgery than men, but the reasons are unclear. The objective of this study is to evaluate the association between pre-operative widespread pain (WP) and failure to experience clinical improvement 2 years following TKR separately for men and women.

Methods:

Osteoarthritis Initiative participants who underwent TKR surgery prior to the 7-year follow-up visit were included in the analysis. WP was defined based on a modified ACR definition of chronic WP and was assessed with a questionnaire which included a homunculus figure. Pain and disability were assessed at the clinic visit prior to TKR as well as 2 years later, using WOMAC pain, WOMAC disability, and Knee Injury and Osteoarthritis Outcome (KOOS) pain scores. Medication use for osteoarthritis (OA)-related symptoms was also determined. Clinically significant improvement was defined as improvement in WOMAC subscale (or KOOS pain) score ≥ to the minimal important difference (based on previously published literature). Relative risk (RR) of no clinical improvement was estimated using log-binomial regression, comparing participants with and without WP, stratified by gender.

Results:

Our sample consists of 120 with and 178 without WP who underwent TKR surgery. Those with WP, compared to those without, were more likely to be women (70.0% vs. 56.2%), with <$50K/year income (48.21% vs. 37.1%), and obese (55.3% vs. 46.8%). Two years after their pre-operative pain assessment, ~12% of men and ~15% of women reported no clinical improvement in knee pain. OA-related medication use after surgery was also more common in women with WP than those without (69.2% vs. 50.0%, p=0.0311).

Among women, WP prior to surgery was significantly associated with an increased risk of no clinically significant improvement following TKR based on WOMAC pain (RR 2.35, 95% CI [1.06-5.20], p=0.0351) and results were suggestive, though not significant, for KOOS pain (RR 1.93, 95% CI [0.97-3.85], p=0.0626). After adjustment for sociodemographic and clinical characteristics, the magnitudes of association were stronger (WOMAC pain, RR 3.50, 95% CI [1.05-11.65], p=0.0409; KOOS pain, RR 2.49, 95% CI [1.00-6.18], p=0.0490). No association among men was observed between pre-TKR WP and failure to improve in WOMAC or KOOS pain score following surgery (Table 1). No strong evidence for an association between WP and failure to improve in WOMAC disability was seen for either gender.

Conclusion:

WP prior to TKR was significantly associated with increased risk of no clinical improvement in knee OA pain 2 years later among women. However, no evidence of an association between WP and TKR outcome was found among men, though the prevalence of WP pain among men was also limited. WP assessment may help identify patients at risk of failure to benefit from TKR surgery.