Methods of stabilizing the sacroiliac joint by placing an expandable device in the joint to generate laterally opposing forces against the iliac and sacral surfaces of the SI joint to securely seat the device in a plane generally parallel to the SI joint. The expandable device is coated with or otherwise contains a bone material to promote fusion of the joint. The expandable device used in methods of the present invention can be, for example, an expandable cage, a balloon, a balloon-expandable stent or a self-expanding stent.