Which factor most directly causes SI fixation?

• A. Ligament adhesions
• B. Disc degeneration
• C. Edema in joint
• D. Myospasm

Answer: (A)

Ligament adhesions within the sacroiliac complex directly create fixation by forming scar tissue that binds the sacrum to the ilium and restricts the natural gliding of the joint. The SI joints rely on their ligaments to provide stability while allowing only small amounts of movement; when adhesions develop in these ligaments or the joint capsule after injury or inflammation, they knit the surfaces together and lock the joint in place. Edema signals acute inflammation and can limit motion temporarily, but it doesn’t produce a lasting mechanical fix. Disc degeneration affects the lumbar discs rather than the SI joint itself, so it doesn’t directly cause SI fixation. Myospasm may hinder movement due to guarding, but it doesn’t structurally fix the joint.