We selected ROR1 as the potential marker gene for tumor cells because MEG8 is a long non‐coding RNA (lncRNA), whereas ROR1 encodes a cell surface receptor closely related to tumor growth, invasion, and metastasis.[36, 37, 38] In addition, we compared the expression levels of ROR1 in other synovial samples and found that ROR1 was rarely expressed in Fbs from OA synovium (Figure S4D, Supporting Information). This evidence concerns the gene CD177 and neoplasm.