Cutibacterium acnes sternoclavicular joint osteomyelitis in an otherwise healthy 55-year-old man.

Sternoclavicular joint osteomyelitis is extremely rare, with only 225 reported cases in the last 45 years. We present an unusual case in an otherwise healthy 55-year-old man with a history of well-controlled type 2 diabetes mellitus and hypertension. He presented to the emergency department after a week of left knee pain that worsened to full-body joint pain with left sternoclavicular swelling. He was started on antibiotics with multiple washouts of the left knee and treated for septic arthritis. By MRI and CT, he was found to have left sternoclavicular joint osteomyelitis and abscess and underwent debridement and resection. We believe that the initial joint injection resulted in haematogenous spread to the left sternoclavicular joint, stressing the importance of a sterile field for joint procedures.