A seated flexion test is negative; the sacral bases are both deep; the ILAs are both shallow. What is the diagnosis?

• A. Left-on-left torsion
• B. Anterior torsion
• C. Bilateral extension
• D. Bilateral flexion

Answer: (D)

When the seated flexion test is negative, the dysfunction is bilateral rather than unilateral. The next step is to compare the pattern of sacral landmarks on both sides. In bilateral dysfunction, two main patterns are possible: bilateral flexion or bilateral extension. In bilateral flexion, the sacral bases are moved anteriorly (sacral bases become deep) and the posterior aspects (the ILAs) are relatively shallow on both sides. The given findings—both sacral bases deep and both ILAs shallow—fit this bilateral flexion pattern. Therefore, bilateral flexion is the best diagnosis.

Bilateral extension would show the opposite pattern (shallower sacral bases and deeper ILAs), and unilateral torsions would produce asymmetry with a positive seated flexion test.