Methods and apparatus for diagnostic and/or therapeutic manipulation of the sacro-iliac joint (SI joint). Trajectories for corridors used to manipulate the target SI joint are also disclosed. In one embodiment, the method comprises palpitating the inferior end of the SI joint, confirming via an imaging technique, and injecting a material into the joint. The injected material (such as a bone forming material) is deposited from the needle or through an implanted catheter. The SI joint may be also immobilized while the fusion mass forms via the use of at least one fixation member. In one embodiment, the fixation member comprises an external member and two internal members which threadedly engage each other. The fixation member is configured to expand and comprises bone growth promoting feature. The expanded member fixates the ilium to the Sacrum on the side of the target SI joint, thus the SI joint is immobilized and fused.
