I.

Purpose The presence of allergies has been proposed as a risk factor for worse outcomes in total knee arthroplasty surgery. The aim of this study is to evaluate if the presence of some psychiatric disorders is more frequent in patients who report allergies and if they could be the main cause for the worse outcomes. Methods A prospective study, including patients undergoing a primary total knee arthroplasty, was designed. In the preoperative visit, all the patients completed a questionnaire about the presence of allergies and also psychiatric tests for anxiety (State‐Trait Anxiety Inventory–STAI‐), depression (Remission from Depression Questionnaire–RDQ‐), somatization disorder (Patient Health Questionnaire‐15–PHQ‐15‐), pain catastrophizing syndrome (Pain Catastrophizing Scale–PCS), and personality disorder (Reduced NEO‐Inventory of Five Factors–NEO‐FFI‐). In the preoperative and at 6 months of follow up, the functional results of the surgery were assessed by the WOMAC, the SF‐12, and the KSS scores. Results A total of 209 patients was included: 136 (65%) did not have reported allergies and 73 (35%) did report some allergies. The psychiatric questionnaires showed that the presence of anxiety was more prevalent in the group of patients with reported allergies (STAI‐T: no allergies 24.08 points vs. allergies 19.18 points, p = 0.039). When comparing the functional outcomes at 6 months of follow up, most of the analyzed scores improved less in the group of patients with reported allergies than in the no allergy‐referred group: WOMAC‐total score (34.37 vs. 40.10 points, p = 0.023), WOMAC‐pain score (6.03 vs. 7.50 points, p = 0.018), WOMAC‐function score (22.97 vs. 27.24 points, p = 0.023), KSS‐knee score (25.37 vs. 33.79 points, p = 0.002), and SF‐12 physical score (7.89 vs. 11.15 points, p = 0.046). The significance of the difference in the outcomes scores in this group was lost after adjusting for anxiety (p > 0.05). Conclusion Allergies reported by patients are confirmed as a risk factor for worse results after TKA surgery. The relationship with anxiety disorder seems to explain the association between self‐reported allergies and sub‐optimal outcomes. Level of evidence II.