Background: The subchondral lamella of the sacroiliac joint (SIJ) auricular surface is morphologically inconsistent, varying inter-individually and side-dependently. These variations have been well documented, however, the morpho-mechanical relationship to sacroiliac joint dysfunction (SIJD) remains unstudied to date. Here, the bone mineralisation density of the iliac and sacral auricular surface subchondral endplate is compared between morphological subtypes, as well as in large and small surfaces, in a cohort comprising SIJD joints and controls.Methods: Computed tomography (CT) datasets from 29 patients with bilateral or unilateral SIJD were subjected to CT osteoabsorptiometry. Sacral and iliac surface areas and posterior angles were calculated and surfaces were classi ed into small (<15 cm 3 ) and large (≥15 cm 3 ) joints and morphological types 1 (>160°), 2 (130-160°) and 3 (<130°), respectively. Mineralisation patterns were classi ed into four patterns, two marginal (M1 and M2) and two non-marginal (N1 and N2). Each sacral and iliac surface was subsequently classi ed into one of these mineralisation groups.Results: The surface area of all joints in the cohort averaged 15.0±2.4 cm 2 (males 16.2±2.5 cm 2 , females 13.7±1.6 cm 2 ). No age correlations with surface area were found nor differences in mean HU values when comparing sizes, sexes or morphology type when looking at painful joints (unilateral or bilateral) and contralateral non-painful joints. Comparisons of controls with the SIJD cohort revealed signi cant differences in female sacra (p=0.02) and small sacra (p=0.03). There was low conformity in marginal and non-marginal patterns, 26% for contralateral non-painful joints, and 46% conformity in painful joints.The majority of dysfunctional joints was of type 2 morphology (59%), equally distributed between small (49%) and large joints (51%). Larger joints had the highest frequency of painful joints (72%). Regarding the prominence of sub-patterns, M1C was more prominent in painful joints.Conclusions: Load distribution related to difference in auricular surface morphology seems to have little impact on pain-related subchondral bone adaptation in cases of SIJD. Larger joints may be predisposed to the onset of pain due to the weakening of the extracapsular structures. Pain-affected joints re ect common conformity patterns of sacral apex mineralisation with corresponding superior corner iliac mineralisation.