Osteoarthritis (OA) and hemophilic arthropathy (HA) are clinically similar, but pathologically distinct conditions which result in joint pain and loss of function. Distinguishing their disease mechanisms is therefore a key step in the development of curative therapy, as opposed to current symptomatic treatments. Aim: To investigate the potential differences in plasma proteomic profile between OA and HA patients. Methods: This pilot cross-sectional study includes N=40 male participants equally divided across 4 subgroups: 1-2/haemophilia patients with severe or mild HA and 3-4/control subjects with severe or mild/no OA. We pooled plasma samples from each stage to search for biomarkers that accurately present each condition in order to achieve a biological sample which would represent a “biological average” as much as possible (1,2). The protein profile will be determined using liquid chromatography / mass spectrometry, after which functional gene enrichment analysis will be performed. Conclusion: The goal of the study is to uncover marked differences in plasma proteomic profile in patients with HA vs. OA which will potentially shed new light on the mechanisms of HA pathogenesis and could identify potential molecular therapeutic or diagnostic targets.