A visible mass around the sternoclavicular (SC) joint may be explained by a wide variety of diagnoses, each with its own diagnostic pathway and treatment options. Here we report three cases: a 56-year-old male with an anterior luxation of the right SC joint, a 59-year-old male with osteomyelitis of the left SC joint and a 78-year-old male with a painless swelling to the right medial clavicle, interpreted as sterno-costo-clavicular hyperostosis (SCCH) as part of his SAPHO syndrome. An atraumatic swelling of the SC joint is most often caused by osteoarthritis, characterized by a slowly progressing solid swelling. Acute swelling with concurrent redness and fever justifies an intra-articular- or bone aspiration, possibly CT guided, in combination with laboratory blood tests to differentiate between an infectious or rheumatologic cause. Since there are also multiple rare diseases that present specifically around the SC joint, a multidisciplinary review often proves helpful.