Reply to the Letter to the Editor: Complications of Total Knee Arthroplasty: Standardized List and Definitions of The Knee Society

Abstract

To the editor: Thank you for your thoughtful consideration of our work on complications of TKA. We agree that pain is an unfavorable outcome following TKA, as TKA is generally proposed in order to relieve pain. We did not include pain in our project because we do not have a generally accepted, standardized definition for pain following TKA, and we did not believe we should develop this definition. Our principal reasons for this belief included: (1) there is no standardized reporting for pain, and unlikely to be one anytime soon because of difference among patients’ perceptions of that symptom, and (2) pain is a symptom, but tells us little about its cause, which can range from aseptic loosening to infection to untreated depression. As you suggest, pain following TKA has been underreported by surgeons. One patient’s severe pain is another patient’s mild discomfort and another patient’s annoyance. Perhaps we should have included pain in our list of exclusions in the Methods and Materials section. Careful evaluation of TKA outcomes notes a higher level of pain than previously recognized and accepted. However, patients’ perception of pain following TKA is not standardized. One patient’s pain level of nine may be another patient’s pain level of one, and both patients report pain. As you note, the incidence of pain following TKA can range from 10% to 34%. The prevalence of pain following could be lower or higher, depending on the population surveyed and the level of pain defined as important enough to measure. Stedman’s Medical Dictionary defines complication as a “morbid process or event that occurs during the course of a disease that is not an essential part of that disease, although it may result from it or from independent causes.” Pain is a symptom that can be caused by a complication or by issues unrelated or related to the TKA. Tachycardia is also a symptom that can be caused by venous thromboembolic disease, but we do not include tachycardia as a complication of TKA. Pain is considered the fifth vital sign, and is an indication of patient outcome. It can be used as an objective standard for judging progress of an individual patient, but is a poor comparator among different patients. At this time, we do not believe that pain following TKA is an easily reported complication which will fit in the TKA complication stratification system. Our work is the first step in understanding and codifying complications and adverse events following TKA. Our patients will teach us more about their complications and adverse events during the next decade. As we continue to listen to our patients, perhaps our list of standardized complications for TKA will be revised.