An ablation catheter (10, 182, 192) comprising: an elongated catheter body (12, 90, 110) extending longitudinally between a proximal end and a distal end (14, 92) along a longitudinal axis; and an electrode assembly (20, 60, 80, 100, 120, 180, 190) connected to the catheter body, the electrode assembly comprising a plurality of spines, each of the plurality of spines having a proximal end connected to the catheter body and a distal end, the distal ends of the plurality of spines being connected to a spine distal junction, wherein each of the plurality of spines includes an intermediate segment, a proximal leg coupled between the intermediate segment and the proximal end and a distal leg coupled between the intermediate segment and the distal end, each of the plurality of spines further including a proximal hinge coupled between the proximal leg and the intermediate segment and a distal hinge coupled between the distal leg and the intermediate segment of each of the plurality of spines, a proximal stiffness change between the proximal end and the intermediate segment of the spine of each of the plurality of spines, and a distal stiffness change between the distal end and the intermediate segment of each of the plurality of spines, wherein each of the plurality of spines includes a plurality of ablation electrodes (22, 62, 82, 102, 122) on the intermediate segments, each of the plurality of ablation electrodes (22, 62, 82, 102, 122) is operable to be energized to produce an ablation zone; wherein the electrode assembly is movable between a collapsed arrangement and an expanded arrangement with the intermediate segments of each of the plurality of spines in the expanded arrangement is configured to move outwardly relative to the proximal ends and distal ends of each of the plurality of spines with respect to the collapsed arrangement; and wherein the ablation electrodes are distributed on the intermediate segments in a staggered configuration such that the ablation zones of the plurality of ablation electrodes span one or more open arc segments around the longitudinal axis, and the ablation zones of all the plurality of ablation electrodes projected longitudinally onto any lateral plane which is perpendicular to the longitudinal axis span a substantially closed loop around the longitudinal axis. an elongated catheter body (12, 90, 110) extending longitudinally between a proximal end and a distal end (14, 92) along a longitudinal axis; and an electrode assembly (20, 60, 80, 100, 120, 180, 190) connected to the catheter body, the electrode assembly comprising a plurality of spines, each of the plurality of spines having a proximal end connected to the catheter body and a distal end, the distal ends of the plurality of spines being connected to a spine distal junction, wherein each of the plurality of spines includes an intermediate segment, a proximal leg coupled between the intermediate segment and the proximal end and a distal leg coupled between the intermediate segment and the distal end, each of the plurality of spines further including a proximal hinge coupled between the proximal leg and the intermediate segment and a distal hinge coupled between the distal leg and the intermediate segment of each of the plurality of spines, a proximal stiffness change between the proximal end and the intermediate segment of the spine of each of the plurality of spines, and a distal stiffness change between the distal end and the intermediate segment of each of the plurality of spines, wherein each of the plurality of spines includes a plurality of ablation electrodes (22, 62, 82, 102, 122) on the intermediate segments, each of the plurality of ablation electrodes (22, 62, 82, 102, 122) is operable to be energized to produce an ablation zone; wherein the electrode assembly is movable between a collapsed arrangement and an expanded arrangement with the intermediate segments of each of the plurality of spines in the expanded arrangement is configured to move outwardly relative to the proximal ends and distal ends of each of the plurality of spines with respect to the collapsed arrangement; and wherein the ablation electrodes are distributed on the intermediate segments in a staggered configuration such that the ablation zones of the plurality of ablation electrodes span one or more open arc segments around the longitudinal axis, and the ablation zones of all the plurality of ablation electrodes projected longitudinally onto any lateral plane which is perpendicular to the longitudinal axis span a substantially closed loop around the longitudinal axis.