In psoas abscess associated with spinal disease, or in disease of the bursa underneath the psoas, the limb is flexed and everted, there may be lordosis, and the patient may limp in walking, but the movements at the hip are restricted only in the directions of extension and inversion, while in hip disease they are restricted in all directions.
"Manual of Surgery Volume Second: Extremities--Head--Neck. Sixth Edition."
Alexander Miles Alexis Thomson
The frame does not interfere with such extension as may be necessary, to the head, for example, in recent cervical caries, or to the lower extremities where flexion at the hip from spasmodic contraction of the psoas muscle may be efficiently relieved by weight-extension.
"Manual of Surgery Volume Second: Extremities--Head--Neck. Sixth Edition."
Alexander Miles Alexis Thomson
U. psoas muscle, supporting the right spermatic vessels.
"Surgical Anatomy"
Joseph Maclise