How can i fix my sacroiliac instability?

Prolotherapy: I have had much success treating sacroiliac (si) & other joint instabilities with prolotherapy - aka 'stimulated ligament reconstruction': injecting si ligaments with a mild irritant (could even be a form of sugar & water). The body 'thinks' it has a new injury and rushes to 'repair' the ligament - laying down new fibers, shortening & strengthening the ligaments. Osteopaths & mds can both do this.

Graded Therapies: Shoe lift on short leg side, sacroiliac joint belt (boa.Com.), soft mattress, yoga (superman posture). Prolotherapy, and in most severe fusion. For more information about this topic see my chronic pain board at quora.Com.

SI Instability: Pain at the si joint is an enigma. There is no observable problem on any test in most cases: ct, mri, bone scan, xray are all usually normal. Make sure you don't have an inflammatory condition (rheumatologist can help). Then, manipulative pt can really help (needs doc's rx). Si injections useful for diagnosis and treatment. Failing above, minimally invasive si fusion useful (rarely needed).