Development and formulation of the classification criteria for osteoarthritis
Original Article

Development and formulation of the classification criteria for osteoarthritis

Cibo Huang1#, Zhiyi Zhang2#, Yaolong Chen3,4#, Yue Zhang5, Dan Xing5, Like Zhao1, Jianhao Lin5, Yifang Mei2, Hsiao-Yi Lin6, Yi Zheng7, Wei-Chung Tsai8, Shengyun Liu9, Quan Jiang10, Yi Liu11, Jinwei Chen12, Zhizhong Ye13, Min Chen1, Yingjuan Chen1, Cong-Qiu Chu14, Ming Gao1, Lan He15, Jin Lin16, Lijun Wu17, Jianhua Xu18, Pinting Yang19, Xuewu Zhang20, Qing Jiang21, Guanghua Lei22, Mengtao Li23, Wanling Yang13, Xin Gu24, Yixin Zhou25, Dongyi He26, Wei Liu27, Weiya Zhang28, Changhai Ding29, Xiaofeng Zeng23; on behalf of the COACH Group

1Department of Rheumatology, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing, China; 2Department of Rheumatology, The First Affiliated Hospital, Harbin Medical University, Harbin, China; 3Evidence-Based Medicine Center, School of Basic Medical Sciences, Lanzhou University, Lanzhou, China; 4WHO Collaborating Centre for Guideline Implementation and Knowledge Translation, Lanzhou, China; 5Arthritis Clinic & Research Center, Peking University People’s Hospital, Beijing, China; 6Veterans General Hospital, Taipei and National Yang-Ming Medical University, Taipei, Taiwan; 7Department of Rheumatology, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China; 8Department of Internal Medicine, Kaohsiung Medical College, Kaohsiung City, Taiwan; 9Department of Rheumatology, First Affiliated Hospital of Zhengzhou University, Zhengzhou, China; 10Department of Rheumatology and Immunology, Guang’anmen Hospital, China Academy of Chinese Medical Sciences, Beijing, China; 11Department of Rheumatology, West China Hospital, Sichuan University, Chengdu, China; 12Department of Rheumatology, Second Xiangya Hospital, Central South University, Changsha, China; 13Shenzhen Futian Hospital for Rheumatic Diseases, Shenzhen, China; 14Division of Arthritis and Rheumatic Diseases, Oregon Health & Science University and VA Portland Health Care System, Portland, OR, USA; 15Department of Rheumatology and Immunology, the First Hospital of Xi’an Jiaotong University, Xi’an, China; 16Department of Rheumatology, First Affiliated Hospital of Zhejiang University, Hangzhou, China; 17Department of Rheumatology, People’s Hospital of Xinjiang Uygur Autonomous Region, Urumchi, China; 18Department of Rheumatology and Immunology, the First Affiliated Hospital of Anhui Medical University, Hefei, China; 19Department of Rheumatology and Immunology, the First Affiliated Hospital of China Medical University, Beijing, China; 20Department of Rheumatology, Peking University People’s Hospital, Beijing, China; 21Department of Osteoarthrosis, Affiliated Drum Tower Hospital, Nanjing University Medical College, Nanjing, China; 22Department of Orthopedics, Xiangya Hospital, Central South University, Changsha, China; 23Department of Rheumatology, Peking Union Hospital, Chinese Academy of Medical Sciences, Beijing, China; 24Beijing Hospital Rehabilitation Medicine, Beijing, China; 25Department of Orthopedics, Beijing Jishuitan Hospital, Beijing, China; 26Department of Rheumatology and Immunology, Shanghai Guanghua Hospital, Shanghai, China; 27Department of Rheumatology and Immunology, Affiliated Hospital of Tianjin University of Traditional Chinese Medicine, Tianjin, China; 28Academic Rheumatology, University of Nottingham, Nottingham, UK; 29University of Tasmania, Tasmania, Australia

Contributions: (I) Conception and design: C Huang, Z Zhang, Y Chen; (II) Administrative support: Y Chen; (III) Provision of study materials or patients: C Huang, Z Zhang, Y Chen; (IV) Collection and assembly of data: W Zhang, C Ding, X Zeng; (V) Data analysis and interpretation: W Zhang, C Ding, X Zeng; (VI) Manuscript writing: All authors; (VII) Final approval of manuscript: All authors.

#These authors contributed equally to this work.

Correspondence to: Weiya Zhang. Academic Rheumatology, University of Nottingham, Room A18, Academic Rheumatology Clinical Sciences Building, Nottingham City Hospital, Hucknall Road, Nottingham, NG5 1PB, UK. Email: weiya.zhang@nottingham.ac.uk; Changhai Ding. Menzies Research Institute Tasmania, University of Tasmania, C. Ding, Private Bag 23, Hobart, Tasmania 7000, Australia. Email: ChangHai.Ding@utas.edu.au; Xiaofeng Zeng. Department of Rheumatology, Peking Union Medical College Hospital, Peking Union Medical College and Chinese Academy of Medical Sciences, No. 41 Damucang Hutong, Xicheng District, Beijing, China. Email: xiaofeng.zeng@cstar.org.cn.

Background: The classification criteria of osteoarthritis (OA) is lack of the support of relevant research evidence and there is no standardized protocol for detailed steps of the development or clinical verification of classification criteria has yet been established. This study aims to describe the development process of the Categorization of Osteoarthritis CHecklist (COACH), which is designed to choose the precise treatment option for patients with OA.

Methods: A multidisciplinary panel was established to gather opinions. We conducted questionnaire survey and literature review to generate and COACH Panel members were invited to review the drafted classification criteria and optimize classification criteria. The final list of items was discussed and reached the agreement by the core group of the panel.

Results: Thirty-six experts participated in COACH Panel including rheumatologist (80.6%; 29/36), orthopedist (13.9%; 5/36), methodologist (2.8%; 1/36) and rehabilitation physician (2.8%; 1/36) for classification factors generating and optimizing. The main body of the final classification criteria consists of six types of OA pathogenesis, eight types of medical findings (which can be grouped into two categories), and six types of the location. The final criteria include load-based type, structure-based type, inflammation-based type, metabolic-based type, systemic factor based type and mixed type.

Conclusions: COACH can better help clinicians quickly classify OA patients and help to choose the best treatment option from the aspects of types, findings and locations. What’s more, the classification criteria are also helpful to promote the basic medical research and targeted prevention of OA.

Keywords: Osteoarthritis (OA); classification; classification factors; survey; literature review


Submitted Jun 12, 2020. Accepted for publication Jul 26, 2020.

doi: 10.21037/atm-20-4673


Introduction

Osteoarthritis (OA) is a leading cause of pain and disability. This multifactorial joint disease is associated with biomechanical, genetic and other factors (1). The prevalence of OA in the elderly aged over 60 is about 10–15% (2). The annual treatment cost of OA is about 3,000 US dollars per person, and the direct and indirect costs account for about 0.25–0.5% of the countries’ GDP (3). OA thus contributes to a huge economic burden to families and the society. In recent years, with the diversification of OA treatment options, the classification of OA to help to select the most appropriate type of treatment has become an increasingly important topic. The existing classification criteria have neither been widely recognized nor used in clinical practice. On the one hand, the classification may lack the support of relevant research evidence, on the other hand, no standardized protocol for detailed steps of the development or clinical verification of classification criteria has yet been established.

To better guide the choice of a precise treatment of OA, The Committee of Rheumatological and Immunological Experts of the Cross-Straits Medicine Exchange Association (SMEA) launched the Categorization of Osteoarthritis CHecklist (COACH) project while developing the 2019 Chinese Guideline for Diagnosis and Treatment of Osteoarthritis (hereinafter referred to as “OA Guideline”) (4). The present article describes the development process of the COACH. We present the following article in accordance with the AGREE reporting checklist (available at http://dx.doi.org/10.21037/atm-20-4673).


Methods

The development of COACH consisted of four phases: (I) panel selection, (II) generation of the classification factors, (III) optimization of the classification factors, (IV) approval of the final criteria.

Panel selection

To gather opinions suggestion on the development of COACH, a multidisciplinary panel consisted of experts in rheumatology, orthopedics, rehabilitation, radiology, and evidence-based medicine from hospitals and scientific research institutions in different regions was convened.

Generation of the initial classification factors

Questionnaire survey

We conducted questionnaire included two main questions: (I) how to classify the OA patients? (II) how to choose treatment based on the classification results for different patients? we analyzed survey results to obtain classification factors by using the framework analysis (5,6).

Literature review

The objective of the literature review was to collate the supporting evidence for classification factors. We searched the MEDLINE, China Biology Medicine (CBM), China National Knowledge Infrastructure (CNKI), Epistemonikos, Cochrane Library and Wanfang database on November 2018 for Chinese or English articles about OA and initial classification factors. Search terms including: “分类标准”, “评估标准”, “临床分型”, “Classification criterion”, “Clinical classification”, “因素”, “暴露”, “预测”, “风险”, “risk”, “factor”, “incidence”, “systematic review”, “Meta”, “系统评价”, “系统综述” and “荟萃分析”. Systematic reviews, randomized controlled trials, cohort studies and case-control studies were systematically searched in order to include high to low quality of evidence from different study types. We included studies reporting any specific data. We summarized the findings of evidence link to classification factors for consensus meeting.

Optimization of the classification factors

A writing group drafted classification criteria. We invited COACH Panel members to participate in consensus meeting and to provide feedback. We reviewed the comments and optimized classification criteria through discussions.

Approval of the final criteria

The checklist was presented and discussed in a workshop at the Academic Annual Meeting of the 6th Cross-Strait Medical and Health Exchange Association Rheumatology and Immunology Committee. In this workshop, we asked the participants to give an overall impression of the checklist. The core group discussed the results and agreed on the final list of items.


Results

COACH Panel

Thirty-six individuals participated in COACH Panel at the conference in Beijing on March 9th, 2018. In total, 32 from 14 provincial administrative regions in China, 4 from overseas. Roles of the panelists were rheumatologist (80.6%; 29/36), orthopedist (13.9%; 5/36), methodologist (2.8%; 1/36) and rehabilitation physician (2.8%; 1/36).

Generation of the initial classification factors

The survey questionnaire results included 10 classification factors from framework analysis. We retrieved 2,872 articles for literature review, from which we included 16 systematic reviews and 20 cohort studies as supporting evidence.

Optimization of the classification factors

The COACH group held two face-to-face meetings with same group of experts, in Beijing on May 25th and in Guangzhou on December 15th, 2018, selected all classification factors and integrated 3 classification factors on the classification model.

Final criteria and supporting evidence

The main body of the classification criteria consists of six types of OA pathogenesis, eight types of medical findings (which can be grouped into two categories), and six types of the location. OA patients are divided into different types according to the pathogenesis (purple boxes), the supporting data next to the box showing the risk ratio of pathogenesis. Medical findings are shown in dark blue circles, and the percentage on the left represent the frequency of OA patients. Treatments are shown in green (basic treatment, the ordinal number is the order in OA Guideline), yellow (medication), orange (surgery) and black (treatment of primary disease) boxes. The location of the disease is represented by a hexagon. The connection between treatments, medical findings and location represents the choice of treatment that should be considered (Figure 1).

Figure 1 Classification criteria for OA. The main body of the classification criteria consists of six types of OA pathogenesis, eight types of medical findings (which can be grouped into two categories), and six types of the location. OA patients are divided into different types according to the pathogenesis (purple boxes), the supporting data next to the box showing the risk ratio of pathogenesis. Medical findings are shown in dark blue circles, and the percentage on the left represent their frequency of OA patients. Treatments are shown in green (basic treatment, the ordinal number is the order in OA Guideline), yellow (medication), orange (surgery) and black (treatment of primary disease) boxes. The location of the disease is represented by a hexagon. The connection between treatments, medical findings and location represents the choice of treatment that should be considered.

Load-based OA

Load-based OA develops mainly due to excessive joint load, occupational risks, exercise, overweight and obesity. This type of OA will exert repetitive stress, is often accompanied by the formation of osteophyte and subchondral cysts, and may result in destruction of articular cartilage. A systematic review from China published in 2017 showed an increased risk of knee OA in excessive joint-loaded populations [odds ratio (OR) =3.29, 95% confidence interval (CI): 1.76–6.15] (7). Another 2017 systematic review showed an increased risk of hip OA in senior athletes, especially handball, football and hockey players (8), and one systematic review showed that the risk of knee OA was increased in professional athletes (OR =1.31, 95% CI: 1.11–1.55) (9). Overweight and obesity can also cause greater load on joints, especially the weight-bearing joints, such as the hips and knees. A 2015 systematic review showed an increased risk of knee OA in overweight (OR =1.98, 95% CI: 1.57–2.20) and obese patients (OR =2.66, 95% CI: 2.15–3.28). About a quarter new cases of knee OA were caused by overweight or obesity (10).

Structure-based OA

Abnormal instability of joint structure, joint deformity or defect, and injury of bone, cartilage, ligament, meniscus and muscle weakness caused by cartilage movement and other factors, can lead to instability of joint structure and biomechanical changes of joint. The incidence of OA with hip dysplasia was found to be 80% (95% CI: 28–99%) (11). A systematic review showed that joint malalignment (12) and arched leg (13) are risk factors for OA. Patients with knee extensor muscle weakness had an increased risk of knee OA (OR =1.65, 95% CI: 1.23–2.21) (14). Knee varus and valgus increased the risk of medial compartment OA (OR =3.59, 95% CI: 2.62–4.92) and lateral compartment OA (OR =4.85, 95% CI: 3.17–7.42) (15). Joint trauma could also lead to abnormal joint structure. The risk of knee joint OA was significantly increased in patients with knee injury history (OR =4.20, 95% CI: 3.11–5.66) (16).

Inflammation-based OA

The inflammatory mediators, mainly caused by various types of inflammatory arthritis (suppurative, tuberculous, and rheumatoid arthritis), may affect synovial cells and result in synovitis and articular cartilage destruction. Inflammation at joint sites may cause OA (17). A cohort study from 2017 showed an increased risk of OA in patients with ankylosing spondylitis (OR =1.43, 95% CI: 1.33–1.54) (18).

Metabolic-based OA

Metabolic-based OA is mainly due to metabolic disorders and changes in the metabolic environment of the joints that lead to obstruction of bone formation, further destruction of articular cartilage and OA. We identified the following specific risk factors: (I) the inflammatory response and high glucose environment caused by diabetes metabolism aggravated the destruction of articular cartilage. A 2017 systematic review (19) showed an increased risk of OA in diabetic population (OR =1.50, 95% CI: 1.10–2.06). (II) There may be common risk factors between hypertension and OA, such as advanced age, obesity and chronic inflammation (20). A 2017 systematic review (20) showed that hypertensive population had an increased risk of OA (OR =1.49, 95% CI: 1.26–1.77). (III) Sodium urate crystals in the joints of gout patients bind to Toll-like receptors in chondrocytes, which affect chondrocyte function, and the pain caused by it may also alter OA biomechanics. A 2016 cross-sectional study (21) showed that gout patients had higher risk of onset of hand OA (OR =1.46, 95% CI: 0.61–3.50), having ≥8 hand joints with moderate to severe OA (OR =3.57, 95% CI: 0.62–20.45), foot OA (OR =2.16, 95% CI: 0.66–7.06), having ≥3 foot joints affected with OA (OR =4.00, 95% CI: 0.99–16.10), and having ≥1 foot joint with severe OA (OR =1.46, 95% CI: 0.54–3.94) than patients without gout. (IV) Calcium pyrophosphate dihydrate (CPPD), which often has similar symptoms than gout, is called pseudo-gout. The pathogenesis of CPPD is still unclear. Many cases of OA patients have CPPD. A case-control study from 1999 (22) showed that patients with CPPD (pseudogout) had an increased risk of OA (OR =13.8, 95% CI: 3.4–59.8). (V) The iron excess caused by hemochromatosis may lead to the inhibition of osteoblast activity and the reduction of bone formation. A 2010 case-control study (23) showed that people with hereditary hemochromatosis had an increased risk of OA (OR =2.5, 95% CI: 1.8–3.6), knee arthroplasty (OR =5.3, 95% CI: 1.1–25.6) and hip arthroplasty (OR =5.2, 95% CI: 2.2–11.9). (VI) Brown yellow disease leads to the accumulation of uric acid and the weakening of collagen, resulting in crevice and degeneration of articular cartilage, which is an important cause of OA joint replacement (24). (VII) Cartilage calcinosis may indirectly lead to cartilage degeneration by increasing matrix hardness. A 2013 cross-sectional study showed that patients with chondromatosis had an increased risk of right knee OA (OR =2.39, 95% CI: 1.79–3.20), right hip OA (OR =1.08, 95% CI: 0.73–1.59), right wrist OA (OR =4.46, 95% CI: 3.24–6.13), left knee OA (OR =2.78, 95% CI: 2.04–3.79), left hip OA (OR =0.72, 95% CI: 0.44–1.20), and left wrist OA (OR =4.42, 95% CI: 3.26–6.00) (25). (VIII) Kashin-Beck disease may increase the incidence of OA. An epidemiological study from 2018 showed that the detection rate of hand OA was 42.3%, and knee OA was 62.5% in patients with Kashin-Beck. In the patient group without Kashin-Back disease, the detection rate of hand OA was 33.3%, and knee OA was 56.6%. The difference was statistically significant (26). (IX) The risk factors of diffuse idiopathic bone hypertrophy (DIH) may also be related to OA. A 2015 population-based cohort study showed that the risk of OA was increased (OR =1.89, 95% CI: 1.14–3.10) (27) with DIH. (X) The risk of OA in patients with acromegaly was also significantly increased (28).

Systemic factor-based OA

This type of OA cannot be associated with any main pathogenic factor. Age is closely related to the occurrence of OA. The incidence of OA in people aged 40 years or above ranges between 10% and 17%, and among people aged 60 years and older the risk at least 50% (29). Potential reasons include the decline of age-related bone regeneration ability and the accumulation of risk factors (1). The risk of OA in women was significantly higher than that in men (OR =1.68, 95% CI: 1.37–2.07) (10), and sex hormones may be the cause of the difference. Decreased estrogen levels caused by ovarian dysfunction can lead to articular cartilage metabolism becoming weaker and inducing OA (30). A cold or humid living environment may also cause OA (31). A 2017 systematic review of the Chinese population showed an increased risk of knee OA among people living in humid environments (OR =5.21, 95% CI: 2.26–12.02) (7). The incidence of OA is also associated with certain genetic factors. Genome-wide association studies have shown that genetic polymorphism was associated with the susceptibility of OA. The British Association of Osteoarthritis Genetics has identified 11 OA-related genes in European populations (32). Two systematic reviews of Asian populations also showed that rs12885713 and rs7639618 gene polymorphisms were significantly associated with increased risk of OA (33,34).

Mixed type

This type is related to several of the factors mentioned above, without any factor being dominant.

Medical findings

The medical findings differ by type of OA. For example, because of subchondral bone hyperplasia, osteophytes and Heberden nodules are more easily detected by imaging examination in load-based OA; limited joint movement, joint deformity and abnormal joint alignment are more common in structure-based OA; and joint pain is more significant in inflammation-based OA. However, because this study has not carried out a survey of the incidence of findings of different types, only the retrieved data reported in the process of developing the classification criteria of the American Academy of Rheumatology (ACR) were presented.

Clinical findings

ACR classification criteria showed that the frequencies of OA pain in knee, hip and hand joints were 90%, 81% and 45%, respectively (35-37). The study of OA classification criteria for hip joint (36) showed that the frequency of limited joint movement was 83%.

Imaging findings

ACR classification criteria showed that the frequencies of osteophytes for hip and knee OA were 89% and 70%, respectively (36,37). The frequencies of joint fluid and joint space narrowing were 91% and 84% for hip and knee OA, respectively (36,37). One study of OA classification criteria for hand joints showed that the frequency of Heberden’s nodes was 31% (35). For knee joints, the frequency of malalignment was 63% (37). The frequency of joint deformity for hip OA was 4% (36).

Disease location

OA may occur in various synovial joints, including the hands, knees, hips, spine (e.g., cervical vertebrae, lumbar vertebrae), elbows, and feet. It may affect multiple joints in one person (38). The decision of treatment options, especially in surgical treatment, depends on the joints that it affects. Specific treatment options are presented in the OA guidelines.


Discussion

In this study, we constructed a framework for OA classification through systematic developing methods. The classification criteria combined classification factors of pathogenesis, findings and locations.

Pathogenesis was the most frequently mentioned and the most popular classification factor. The other were medical findings, treatments and location. After this, we built a preliminary classification model according to the relationship between the factors. There are differences in the frequency of medical findings in patients with different pathological causes. The treatment options should be chosen based on the medical findings. Part of the treatments are restricted to certain locations of OA.

The main future directions for the development of this classification criteria include: (I) exploring the pathological mechanism and frequency of OA, (II) studying the proportion of patients with different types of OA, (III) investigating the frequency of medical/clinical findings in patients with different types of OA, (IV) conducting clinical research to verify the application effect of classification criteria, and (V) further analyzing the relationship among treatments, findings and location.


Conclusions

This classification criteria can help clinicians quickly classify OA patients through the results of consultation, and they are also of great significance to early interventions for OA. Through the classification criteria and the OA guidelines, clinicians and patients can choose the best treatment option according to the types, findings and locations. In addition, the classification criteria are also helpful to promote the basic medical research and targeted prevention of OA.


Acknowledgments

We thank Nan Yang, Yanfang Ma, Jingyi Zhang, Jianjian Wang, Qi Zhou, Xufei Luo, Meng Lv and Zijun Wang of Lanzhou University for literature reviewing. We thank Janne Estill, Institute of Global Health of University of Geneva for providing guidance and comments for our classification criteria.

Funding: This study was supported by National Key R&D Program of China (2018YFC1705503).


Footnote

Reporting Checklist: The authors have completed the AGREE reporting checklist. Available at http://dx.doi.org/10.21037/atm-20-4673

Data Sharing Statement: Available at http://dx.doi.org/10.21037/atm-20-4673

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at http://dx.doi.org/10.21037/atm-20-4673). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.


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Cite this article as: Huang C, Zhang Z, Chen Y, Zhang Y, Xing D, Zhao L, Lin J, Mei Y, Lin HY, Zheng Y, Tsai WC, Liu S, Jiang Q, Liu Y, Chen J, Ye Z, Chen M, Chen Y, Chu CQ, Gao M, He L, Lin J, Wu L, Xu J, Yang P, Zhang X, Jiang Q, Lei G, Li M, Yang W, Gu X, Zhou Y, He D, Liu W, Zhang W, Ding C, Zeng X; on behalf of the COACH Group. Development and formulation of the classification criteria for osteoarthritis. Ann Transl Med 2020;8(17):1068. doi: 10.21037/atm-20-4673