隨著人口逐漸老化，自1993年65歲以上人口比例首度超過7%，我國已宣告邁入高齡化國家，至2016年依內政部統計處統計，我國65歲以上老人已佔人口比例13.13%，而老年人常深受慢性疾病所苦，其中退化性關節炎病人更有顯著增加的趨勢，隨著年紀增長，關節疼痛與活動受限程度會逐漸加劇，嚴重影響老年人的生活品質；而退化性關節病變中又以膝關節退化性關節炎最為常見，因此在老年人關節的健康促進與維護上，對於膝退化性關節炎的正確認知就顯得格外重要。透過衛生教育、正確醫療知識的解說傳遞除了幫助病人了解疾病的診斷，改變因醫療常識不足而引起的偏差認知外，更因為有了正確充分的了解，進而能幫病人做出更適當的醫療選擇。
醫療共享決策(Shared Decision Making, SDM)，最早是1982年在美國實施以病人為中心，照護的共同福祉計畫上，為促進醫病相互尊重與溝通而提出其核心價值乃是希望醫病雙方能共享醫療實證結果，讓病人能由醫療團隊端得到高品質的醫療資訊，並著重醫病和諧與相互尊重的態度，加入病人的期待及個人考量。目的是讓醫療團隊人員與病人在進行醫療決策前，能因共享優質的實證結果，參酌病人的期待與考量，共同做出符合病人其偏好與利益的醫療決策。
本研究架構融合Dodds and Monroe(1985)的知覺價值理論與Fishbein and Ajzen (1985,1991)的計畫行為理論(Theory of Planned Behavior; TPB)為基礎，以行為態度、主觀規範、知覺價值、行為意願及實際選用行為為架構探討膝退化性關節炎病人面對選擇是否接受人工全膝關節置換手術之影響及在醫療共享決策下是否影響接受人工全膝關節置換手術治療的行為分析，另外加上社會人口因素，來驗證這些變數對接受人工全膝關節手術的醫療行為是否有顯著影響。
本研究問卷包含為社會人口基本資料、對疾病的認知與治療決定等問項方向，歸納出知覺價值、行為態度、主觀規範、行為意願及選用行為各面向結果；經由問卷調查210位膝退化性關節炎病人得到有效問卷186份；回收率94.28%；運用SPSS及E-view統計軟體以線性機率模型(Linear Probability Model, LPM)進行實證分析，建立迴歸方程式進行變數討論。主要的研究結論如下：
一、驗證經醫療共享決策過程後選擇接受人工全膝關節置換手術之〝知覺價值〞、〝主觀規範〞、〝行為意願〞及〝選用行為〞呈正向顯著影響，顯示病人對經過醫療共享決策，可以自醫療團隊端獲得高品質的醫療資訊，也因增加了彼此的了解，而加強醫師了與病人間的雙向互動與信賴，對提升相關醫學知識，縮短認知差距，減少溝通障礙有所幫助，進而加強病人對醫師的信賴度與醫囑遵從性，對選擇接受人工全膝關節置換手術治療有顯著之影響。
本研究亦發現當病人面臨醫療需求時多半會尋求親朋好友之意見幫助，同時也希望在進行是否接受手術治療的抉擇時能有充分表達竟見及自身因素考量自主性，以上驗證，顯示病人對經醫療共享決策後做出是否接受人工全膝關節置換手術的決策有較高的認同感。
二、驗證部分〝知覺價值〞、〝行為態度〞與〝主觀規範〞，呈現負向顯著影響，顯示病人在面臨疾病診治時，多對於原診治醫師有較高的認同感與信賴度，不會隨便改變就醫習慣，至於名醫的加持提升病人選擇手術的意願，驗證結果是不成立。
以上結果，可能因個人背景及疾病嚴重度不同而會有不一樣的選擇。

SUMMARY
This study focused on whether patient engagement in shared decision making (SDM) would affect patients’ decision on receiving total knee replacement.
Based on the perceived value theory proposed by Dodds and Monroe (1985) and theory of planned behavior proposed by Fishbein and Ajzen (1985,1991), this study explored effects of attitude-toward-behavior, subjective norms, perceived value, behavioral intention on knee osteoarthritis patients’ decision making for receiving total knee replacement, and analyzed factors in decision making for receiving total knee replacement.
Participants of this study were the orthopedic patients from Chiali Chi Mei Hospital, a total of 210 questionnaires with knee osteoarthritis; the response rate was 94.28 %, among which 186 questionnaires were effective. E-view is adopted for empirical analysis with regression model set up for discussion. The research as follows.
1. Such result implied that interaction and reliability between doctors and patients were strengthened through SDM as patients’ medical knowledge was strengthened, while knowledge gap narrowed and communication obstacles cleared. As a result, the reliability and compliance were enhanced.
2. It is found that patients had a higher tendency to agree with and rely on the original doctor, therefore the result failed to support the hypothesis that eminent physicians could raise patient’s willingness for operation.
Keywords: Knee osteoarthritis, total knee replacement, shared decision making (SDM), theory of planned behavior, perceived value theory.

INTRODUCTION
Population aging is happening across the world, and Taiwan officially entered the aging society in 1993 with elderly people aged 65 and over accounted for more than 7% of its total population. In the year 1996, the percentage was already over 13%. With an aging population that continues to grow, increasing prevalence of chronic disease has seen osteoarthritis become one of the major threats to cause disability and health risk to the elderly.
However, over the last ten years, most researches on knee osteoarthritis are mainly focused on the disease itself, treatment, occupational and sport rehabilitation, little literature has been published on cognition of the disease, patient’s feeling, adaption, and choices and obstacles faced during the course of medical treatment. The lack of aforementioned information has led to the cognitive gap between doctors and patients, and the failure to fill the gap between medical service and patient requirement. Through health and medical knowledge education, patients would be able to understand more about the diagnosis and reduce bias due to lack of medical knowledge, which in turn helping them make better medical decision.
MATERIALS AND METHODS
This study focused on whether patient engagement in shared decision making (SDM) would affect patients’ decision on receiving total knee replacement. An empirical analysis was conducted to explore the factors in decision making for medical treatment of osteoarthritis. The selection of medical treatments for knee osteoarthritis, including non-surgical treatments and surgical treatments, are determined by the severity of the disease.
Hence, how to ensure comprehensive communication and build up partnership between doctors and patients for the most appropriate medical decision making is important and necessary.
Participants of this study were the orthopedic patients from Chiali Chi Mei Hospital, This study was designed to answer the question: whether patient engagement in shared decision making (SDM) would affect patients’ intention for receiving total knee replacement. An empirical analysis was conducted to explore the factors in decision making for medical treatment of osteoarthritis, with linear probability model (LPM) applied to analyze variances including perceived value, attitude-toward-behavior, subjective norms, behavioral intention and individual factor. Participants diagnosed with knee osteoarthritis (M196) with International Classification of Disease (ICD-10) were selected to conduct a convenience sampling. In sum, a total of 210 questionnaires were given out, of which 198 were completed in full, with 12 ineffective questionnaires and 186 effective questionnaires. The collection rate of the questionnaire was 94.28 %.
The study framework is built on the analysis of perceived value, attitude-toward-behavior, subjective norms, behavioral intention for receiving total knee replacement, while using demographic variable as the operational definition and measurement to quantify operation mode with LPM and regression analysis as to statistically analyze whether patient engagement in shared decision making (SDM) would affect patients’ intention for receiving total knee replacement.
RESULTS AND DISCUSSION
The results derived from LPM and regression analysis are as follows:
1. The engagement in shared decision making (SDM) has a significant effect on receiving total knee replacement, and SDM also strengthens the interaction and reliability between doctors and patients.
2. Doctors’ explanation and suggestion has a significant effect on patient’s decision on receiving total knee replacement, as patients would gain relevant medical knowledge, while cognitive differences and communication obstacles would be eliminated.
3. The engagement in shared decision making (SDM) has significant effect on receiving total knee replacement, as patients would know more about the effectiveness of the treatment and negative effect of complication.
4. When knee osteoarthritis is so severe that a surgery is required, patients’ decision has a significant effect on receiving total knee replacement.
CONCLUSION
Most patients’ knowledge for diseases comes from the media, relatives and friends as well as doctors’ explanation. Once patients are diagnosed with knee osteoarthritis, they would actively seek for information about the disease, and would also desire detailed explanation from doctors. In this regard, the first priority for the patients and doctors is to work together for the best medical choice through SDM, while helping the elderly seek medical care and learn self-care, providing clear and brief medical information, and respecting patients’ value, preference and opinions are also important. In Taiwan’s medical system, doctors are responsible for attending and taking care of many patients, patients and their family usually hope to receive comprehensive empirical-based information from doctors, but ignore the academic gap between medical professionals and the ordinary. Through health education and medical knowledge illustration, patients would be able to face diseases at ease, accept the diagnosis, change the attitude toward illness, and even make more appropriate medical choice with adequate understanding of the disease, and receive satisfied medical results at last.

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