The primary objective of this study is to evaluate the usability and clinical utility of the Synovasure® RISC™ Panel.

The secondary objective of this study is to create a repository of well-characterized synovial fluid samples from patients with knee pain and/or inflammation to be used for future research.

The Synovasure® RISC Panel™ constitutes a single source of pre-operative biomarker testing with high predictive value for the diagnosis of single or multiple arthritis conditions, that may correspond to a relative level of inflammation and post-operative complication and infection risk in patients with knee pain and/or inflammation.

The aim of this clinical performance post-market clinical follow-up (PMCF) study is to evaluate the usability and clinical utility of the Synovasure® RISC Panel™ using comparative analyses between the suspected diagnosis, patient demographics, conditions, symptoms, medical history and the Synovasure® RISC Panel™ results. The secondary objective of this study is to create a repository of well-characterized synovial fluid samples from patients with knee pain and/or inflammation to be used for future research.

Investigators will perform arthrocentesis as part of the patient's standard of care. Remnant samples will be transferred in the tubes included with the Synovasure® Arthritis Specimen Transportation kit, in accordance with instructions and the requisition form. Additional case report forms (CRFs) to collect demographic, and clinical data beyond what is included in the requisition form and the Panel results accession identification (ID) will be provided. Sample collection and shipment to CD Laboratories (CDL) may be limited to Monday-Wednesday. A maximum of three samples per transportation kit will be shipped as soon as the samples are collected. CDL will perform RISC™ Panel testing and identifiable results will be provided to enable the centers to pair the test results with clinical outcome data. De-identified leftover remnant samples will be frozen and all data, including any available clinical outcome data, will also be entered into a de-identified database of results and made accessible to all participating investigators for research purposes.

Inclusion Criteria:

• Patients with knee pain and/or inflammation and planned arthrocentesis

Exclusion Criteria:

• Patient is unwilling or unable to give oral consent
• Patient has any condition that would, in the judgment of the Investigator, place the patient at undue risk or interfere with the study
• Patient is a vulnerable subject (prisoner, mentally incompetent or unable to understand what participation to the study entails, a known alcohol or drug abuser, anticipated to be non-compliant)
• Patient had an arthrocentesis of the index joint less than 2 weeks from the planned arthrocentesis
• Insufficient synovial fluid sample of < 1.5 mL
• Patient age < 18 or > 89

Patients experiencing knee pain and/or inflammation.