Background: Physical activity (PA) is an important component in the management of Rheumatoid Arthritis (RA). To date the correlates of PA have not been thoroughly investigated in the RA population. The aim of this systematic review was to determine the correlates of PA in the adult RA population. Methods: A search of Medline, EMBASE, AMED, CINAHL plus, Pubmed, Web of Science, and the Cochrane Library was conducted. A manual search of reference lists was conducted to compliment the electronic search. Ten studies fulfilled the inclusion criteria and were assessed for methodological quality. Results: Results determined correlates in 4 categories: sociodemographic, physical, psychological and social variables. The variables varied greatly and were inconsistently studied. Changes were noted from a previous review in 2005 in relation to the association between certain variables and PA, including age, gender, disease duration, pain, exercise beliefs and social support. Conclusions: Positive associations with PA were found for motivation, self-efficacy, health perception, and previous PA levels. Negative associations were found for fatigue, a coerced regulation style and certain physiological variables. In addition differences between correlates of PA in the adult RA population and other chronic disease and healthy adult populations have been demonstrated.