[1] George Inst Int Hlth, Musculoskeletal Div, Sydney, NSW, Australia
[2] Univ Sydney, Fac Hlth Sci, Back Pain Res Grp, Sydney, NSW 2006, Australia
[3] Univ Sydney, Sch Publ Hlth, Sydney, NSW 2006, Australia
[4] Royal Prince Alfred Hosp, Dept Rheumatol, Sydney, NSW, Australia