More infected cases periprosthetic joint infections (PJI) are seen with increasing number of arthroplasty procedures. Despite many tests are available, diagnosis of PJI remains a challenge and a more systematic approach is required. A comprehensive medical history including risk factors for infection, physical examination, erythrocyte sedimentation rate and serum C-reactive protein levels, and also appropriate radiographs are the first line screening tests. Joint aspiration has a high value in the diagnosis of PJI. Aspirates which should be immediately transferred into pediatric blood culture bottles for cultures, should also be sent for synovial leukocyte count and polymorphonuclear percentage. Recently, it has been shown that some biomarkers in the synovial fluid exhibit a higher accuracy in diagnosis of PJI despite patients with the systemic inflammatory diseases and those receiving antibiotic treatment. These synovial fluid biomarkers are expected to overcome the challenges in diagnosis of PJI.

In summary, the diagnosis of PJI is the key for planning and the success of the treatment. While there is no specific diagnostic test recently, studies have begun to inform threshold levels of the synovial fluid biomarkers. In the near future a preoperative diagnosis of PJI would be easier with the widespread commercial use of these tests.