In most cases of SI joint dysfunction, the lower back is painful. The pain may be mild but can also become severe. The pain sometimes spreads into areas like the buttocks and hips and the side or back of the thigh. If the pain is felt beyond the lower back, it may be a sharp stabbing pain similar to that felt with sciatica. In addition, the areas impacted by the sacroiliac joint dysfunction may feel stiff, and the pain will intensify when pressure is placed on the sacroiliac joint.