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The article entitled “Serum and knee synovial fluid matri xmeta llopr otein ase-1 3 and tumor necrosis factor-alpha levels in patients with late stage osteoarthritis" published in Acta Orthopaedica Traumatologic Turcica 2016; 50(6): 670-673 , by Özler K, Aktaş E, Atay Ç, Yılmaz B, Arıkan M, and Güngör Ş.” was unintentionally published twice in May 2016 and November 2016 issues. The second publication in November 2016 issue has been retracted by the editorial office of the Acta Orthopaedica et Traumatologica Turcica. This error occurred in the transition period of the journal and the authors were informed of this mistake and retraction. We apologize for any inconvenience that may have been caused.