Flowchart for case-control matching method. Solid arrows represent patients included in our case-control cohort, whereas dashed arrows and circular nodes represent patients excluded from our case-control cohort. One-to-one case-control matching uses a combination of propensity score and exact matching on the baseline clinical variables of age, body mass index, sex, and ethnicity to create the final cohort. KR = knee replacement, OAI = Osteoarthritis Initiative, PKR = partial knee replacement, TKR = total knee replacement.