Accurate diagnosis of sacroiliac joint (SIJ) pain is challenging. Diagnosis can be aided by pain referral patterns, historical features, physical examination maneuvers, and imaging. However, all of these diagnostic tools have limitations. The most reliable clinical tools may be a combination of three or more positive physical exam maneuvers, although the evidence is inconsistent even for this strategy. Intra-articular diagnostic SIJ injections are often used as the reference standard for "true" sacroiliac pain. However, such injections do not consider extra-articular sources of pain that may also exist as part of the sacroiliac joint complex. Research has established the posterior sacral ligaments as a possible source of pain, and the innervation of these ligaments has been anatomically defined. It is possible that by expanding our focus from the articular portion of the sacroiliac complex structure to both the joint and extra-capsular ligaments, advancements in clinical diagnosis and treatment will be possible.