Psoas sign

Overview
Elicited by the iliopsoas test, the psoas sign is an indicator of irritation to the iliopsoas group of hip flexors in the abdomen.

Physical examination technique
The test is performed by passively extending the thigh of a patient with knees extended. In other words, the patient is positioned on his/her left side, and the right leg is extended behind the patient. If abdominal pain results, it is a positive psoas sign.

Differential diagnosis of causes of a positive psoas sign
Because the right iliopsoas muscle lies under the appendix when the patient is supine, a "positive psoas sign" may suggest appendicitis.

It could also be done by flexing the hip to 90 degrees -- with flexed knee -- asking the patient to actively flex their thigh against resistance.