In this study, joint aspirate of patients that undergo joint aspiration in the context of routine pre- and intra-operative clinical diagnosis of a hip, knee or shoulder joint is collected. Routine joint punctures at our clinic are regularly performed in the emergency room, in the outpatient clinic and intra-operatively during diagnostic and revision surgery. A minimum of 5 ml aspiration fluid was required for inclusion in this study. Empty or diluted aspirations were excluded.