psoas sign

The psoas sign is tested in two ways: (1) passively extending the patient's right hip while they lie on their left side, or (2) having the patient actively flex the hip against resistance while supine. Pain in the right lower quadrant during either maneuver suggests irritation of the iliopsoas muscle, which lies in the retroperitoneum near the appendix. This is especially useful in detecting a retrocecal appendix, which may not produce classic McBurney's point tenderness or peritoneal signs like rebound tenderness, since the inflamed appendix lies posterior to the cecum and is not in direct contact with the anterior peritoneum. Other retroperitoneal or psoas-adjacent pathologies—such as psoas abscess, retrocecal appendicitis, or less commonly diverticulitis—can also produce a positive psoas sign. It is often considered alongside other appendicitis-related signs: obturator sign (pain with internal rotation of flexed hip, suggesting pelvic appendix irritating obturator internus), Rovsing's sign (RLQ pain with palpation of LLQ), and McBurney's point tenderness. While clinically useful, the psoas sign has moderate sensitivity and specificity and should be interpreted in the context of the full clinical picture, including labs (leukocytosis) and imaging (ultrasound or CT), which remain more definitive for diagnosing appendicitis.