Septic arthritis is difficult to diagnose because clinical presentations overlap with non infectious causes and laboratory, imaging, synovial and blood tests are insensitive. Although relatively uncommon, septic arthritis can be severely destructive to joints so the impetus is to give treatment without delay, often prior to a definitive diagnosis. This means patients can undergo invasive procedures, hospital admissions and antibiotics unnecessarily. This brings attendant risks in expanding antibiotic resistance and expense. This study aims to identify biomarkers in blood, urine and synovial fluid that are unique to patients with septic arthritis in order to aid in the rapid and accurate stratification of the acute joint presentation.

Primary objective: To identify blood, urine and synovial fluid biomarkers that are unique to patients with septic arthritis.

Secondary Objective: To determine, through whole genome sequencing of bacterial isolates, whether they are unique to septic arthritis and if there are any molecular signatures associated with a poor structural and systemic prognosis.

Sample: Adults presenting to the Emergency department with likely septic arthritis in one joint or more.

Target: 100

Trail design: Cross sectional proof of concept study