Progression of health‐related quality of life of patients waiting for total knee arthroplasty

Abstract Background Total knee arthroplasty (TKA) remains the surgical gold standard treatment for patients suffering from end‐stage osteoarthritis (OA) of the knee. However, due to the high demand and scarce medical resources, the waiting time for surgery is astoundingly lengthy. Controversies are shown in numerous studies, on whether physical functionality and mental status decline or remain stable over the waiting period. This study aims to evaluate the progression in patients suffering from end‐stage OA while on the waiting list for TKA. Methods One hundred and twenty‐seven patients suffering from end‐stage OA who were on the TKA waiting list were prospectively recruited from our orthopaedics specialist clinic. They were assessed once a year for 2 years or until surgery. The Western Ontario and McMaster University Osteoarthritis Index (WOMAC), SF‐36 self‐rated questionnaire and 15D health‐related quality of life (HRQoL) questionnaire were used as outcome measurements for functionality and disability assessment. Results Patients on the waiting list for TKA showed a progressive increase in pain and disability level within the first year (P = .035). Those patients waiting for more than 2 years showed worsening HRQoL (P < .05) as time progressed. However, no significant difference was observed between the first and second years. Conclusions A decline in functionality and increase in disability were shown in follow‐up assessments conducted every year. However, a plateau effect is observed with end‐stage disease. This emphasizes that more active conservative management programmes should be introduced and implemented while patients are enlisted on the TKA waiting list. Moreover, timely surgical intervention can improve patients' overall function. Trial registration This study involved human participants and reports health‐related outcomes concerning the HRQoL in patients with end‐stage OA of the knee. Thus, it was registered, retrospectively, as a clinical trial under the U.S. National Library of Medicine ClinicalTrials.gov (https://clinicaltrials.gov/) on March 4, 2018.


| INTRODUCTION
Osteoarthritis (OA) is one of the most common chronic degenerative joint disorders in the ageing population. It limits joint movements, induces pain and stiffness, and often leads to exacerbation in the surrounding degenerative changes to tissues, causing disability over time. The prevalence of radiological knee OA rises in proportion with age and sex. The estimated generality of OA knee joint disease is commonly reported as 64.1% and 71.4% in those aged 60 and 70 years and above, respectively, while females have a greater prevalence rate than men. 1 OA patients often encounter swelling, stiffness and pain in their lower extremities, and they usually respond to these symptoms by decreasing physical activities, leading an overly sedentary lifestyle. 2,3 In turn, this inactivity often leads to muscle loss and weight gain. Disease progression is usually slow, but patients become more symptomatic in the end stage of the condition and consequently suffer more pain and disability. 4 Total knee arthroplasty (TKA) is a common procedure for end-stage knee arthritis that has shown significant improvement in terms of functionality, pain and quality of life. [5][6][7][8][9] It remains the gold standard treatment for severe OA of the knee and has gained much public awareness in most third-world developed countries. In places like Hong Kong, the local public health care system provides TKA procedures at a very low cost, but with limited resources, it is often difficult to keep up with the demand from an ageing population. 10 Delaying surgery would further deteriorate bodily functions. Years of postponement deprive patients of the full beneficial potential of TKA, reducing the mobility function in rehabilitation. 11 The present study facilitates the demonstration of evidence-based management with timely knee replacement intervention practices at the level of consensual decision-making by the orthopaedic surgeon.
Patient-reported outcome measures (PROMs) have been used widely in studies to assess outcomes in osteoarthritic patients, [12][13][14] and have shown an exceptional improvement in communication and better decision-making between doctors and patients in addition to improving patient satisfaction with care. [15][16][17][18][19] Most if not all of these measures have displayed favourable amounts of validity and reliability, which are necessary for appraising patient knee functionality and health-related quality of life (HRQoL). Any difference in HRQoL or self-perceived knee functionality is potentially crucial for conducting a comprehensive assessment of OA in both a clinical and research setting; understanding the difference would enable health care providers to have a more comprehensive understanding of the impacts of chronic disease from the patient's perspective and, most importantly, deliver a more holistic health care service.
The aims of this study were to investigate whether there are any differences in symptomatic knee OA patients in regard to their HRQoL, self-perceived knee functionality and their mental status while waiting for a TKA procedure over an extended period.

| MATERIALS AND METHODS
All procedures performed in studies involving human participants were performed in accordance with the ethical standards of The Joint  Over 300 patients with OA symptoms of the knee were screened for study eligibility; a total of 127 patients were recruited at baseline.
Consecutive clinic consultations facilitated the collection of follow-up data; when clinical attendance was not observed, HRQoL and behaviour status of research subjects were determined by a telephone evaluation survey. A few patients refused to spend their time on the telephone survey; those were treated as incomplete or lost to follow-up.

| OUTCOME MEASURES
The outcome measurements for this study are represented by the symptoms, functionality scores and self-rated HRQoL represented by two separate questionnaires. The 36-Item Short Form Survey version 2 was used to measure HRQoL, while the Western Ontario and McMaster Universities Osteoarthritis Index was administered to measure patients' pain and functionality. Assessments were conducted on the first day when recruited to the study. Subsequent assessments were carried out at 1 year and 2 years after the first assessment. Participants that were unable to attend their yearly consultation were then contacted via telephone by research staff to carry out the assessment and inquire about their current HRQoL and behavioural status.

| 36-Item Short Form Survey version 2
The 36-Item Short Form Survey version 2 (SF-36v2) is an instrument designed to measure health concepts relevant across age, disease and treatment groups. It is a validated instrument that has been administrated often to measure the HRQoL and disability in different cohorts. 20 The questionnaire uses 36 separate questions that involve the patient's physical difficulty, functionality, and social and mental

| STATISTICAL ANALYSIS
The data collected were analysed using IBM SPSS Statistics 20. Normality of the data was assessed manually. Age, body mass index and duration of symptoms were entered as continuous variables; others were entered as binary categorical variables. Descriptive statistics including mean and standard deviations were calculated and reported for all SF-36 and WOMAC sub-domains collected from patients' follow-up. An ANOVA with repeated measures was used to compare the differences between each yearly follow-up.

| RESULTS
A total of 127 patients were recruited initially. However, as it was not possible to contact a few patients, the dataset of fully completed records was statistically processed for 86 patient participants. The

| Western Ontario and McMaster University Osteoarthritis Index
Patients showed a statistically significant difference in total and percentage score in their first-(total, +8.44, P = .00; percentage, +8.79, P = .00) and second-year (total, +11.59, P = .00; percentage, +12.08, P = .00) follow-ups (Table 2). They also showed a significant worsening in both pain and functionality scores. In regard to the pain score domain, patients showed a significant average increase of 1.24 in their first year (P = .00) and a higher pain score, with a significant increase of 2.08 compared to the initial value (P = .00). For physical functionality, patients showed an increase in disability at their first-year followup, with a 6.80-point increase (P = .00) and even greater disability in their second year, with a significant increase in disability score of 9.16 compared to their initial score (P = .00). In addition, no significant difference was measured within stiffness score domains at either follow-up.

| DISCUSSION
The present study investigates the health status and HRQoL of patients with OA while waiting on the surgical waiting list for TKA.
During the prolonged period of queuing, they often undergo a tre-

| CONCLUSION
This study has generated valuable clinical implications and given evidence-based information for the medical field and policy makers to reconstruct the current health care system. Based on the data obtained, it is suggested that the waiting time for joint replacement surgery should not exceed 2 years to prevent a further deterioration of pre-operative status among patients with end-stage knee OA and maximize their potential post-operative functional outcomes.

CONFLICT OF INTEREST
The authors declare no competing interests.