Traction radiography of the hip and fluid in the hip joint.

Applying traction to the hip joint normally creates a 'vacuum phenomenon' between the femoral head and the acetabulum. With the presence of fluid in the hip joint, this effect does not occur. Traction radiography thus gives the clinician and radiologist an easy and noninvasive method for detecting fluid in the hip joint. The subsequent article illustrates the potentialities of traction radiography in several hip diseases.