Cho SK, Jung SY, Choi S, et al. - Using the Korean nationwide claim database, knee OA persons between 2013 and 2015 were selected in order to examine factors correlated with the use of opioids as an early treatment choice for knee OA individuals. Among a total of 2,857,999 knee OA people, 12.2% (n = 348,516) were treated with opioids as their primary treatment. In Korea, 12.2% of knee OA persons were treated with opioids as a primary treatment, and tramadol was used more often compared with more powerful opioids. Male gender and comorbidities like depression or musculoskeletal disease were patient factors related to the early use of opioids in people with knee OA.