Unilateral sternoclavicular arthritis: inflammatory arthritis or septic arthritis, that is the question – a case report

Sternoclavicular (SC) joint inflammatory arthritis and septic arthritis can have very similar presentations and can be indistinguishable if a joint fluid aspiration sample cannot be obtained. Septic arthritis of the SC joint accounts for less than 1% of all joint infections. Diagnosis is usually made on the basis of the clinical history combined with elevated infection markers in the blood, specific imaging findings, and most importantly, a positive joint aspiration bacterial culture. To make a diagnosis of SC joint septic arthritis, a high index of suspicion is generally necessary. We herein present the case of a previously healthy 52-year-old man with a 10-day history of left SC pain who improved transiently with anti-inflammatory oral medication; however, the pain subsequently increased over the next 10 days. Follow-up magnetic resonance imaging of the left SC area revealed fluid in the joint with an abscess adjacent to the joint, which was aspirated, and the sample yielded a positive Streptococcus agalactiae culture. Septic arthritis of the left SC joint was diagnosed, and the patient was treated surgically. This case highlights the initial challenges of distinguishing inflammatory from septic arthritis in joints in which a sample for bacterial culture cannot be easily obtained.