During the Thomas Test, how does the therapist assess iliopsoas tightness?

In the Thomas Test, the assessment of iliopsoas tightness is conducted by observing the position of the leg during the test. When a patient lies supine on a table and pulls one knee toward the chest, a tight iliopsoas muscle will prevent the opposite leg from lying flat against the table. If the leg rises off the table during this maneuver, it indicates positive iliopsoas tightness or a contraction of the iliopsoas muscle.

The mechanism of this test relies on the fact that the iliopsoas is a major hip flexor, and when it is tight, it limits the ability of the hip to extend fully. This results in the raised position of the leg that is not being actively drawn toward the chest, as the tightness prevents a relaxed or neutral position.

Therefore, observing the leg rise off the table during the Thomas Test is a clear indicator of iliopsoas tightness, providing valuable information for the assessment of the hip's range of motion and flexibility.