SCJ osteoarthritis: The significance of joint surface location for diagnosis.

An evaluation of the method used to diagnose sternoclavicular joint (SCJ) osteoarthritis (OA) in skeletal remains is presented, with particular attention given to the anatomy of the joint. The current palaeopathological diagnostic criteria used to identify SCJ OA were found to be appropriate for both the sternal and clavicular surfaces of the SCJ, with eburnation indicating perforation of the intra-articular disc and advanced disease. Eburnation was found to occur rarely in the SCJ, and if used as the sole diagnostic criterion would result in an underestimation of SCJ OA prevalence in archaeological assemblages. A key finding was the identification of changes characteristic of OA but confined to the attachment zone of the intra-articular disc on the clavicular surface of the SCJ. As this area of the joint is non-articular, and not normally covered with articular cartilage, a diagnosis of OA would be inaccurate and instead it should be considered as an enthesopathy. It is likely that SCJ OA has been incorrectly identified and over-diagnosed in the archaeological record in the past. More histological research into the disc attachment and its degeneration is required before this can be confirmed.