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.