Thomas test is used for testing?

Hip flexion REF: Lange book of Ohopedics and Spos Medicine Thomas Test: With the patient lying supine, maximally flex both hips. Allow the femur on the ipsilateral side to fall into as much extension as possible, while holding the other hip up. The angle between the femur and examining table is the residual flexion and represents the flexion contracture. REF : Maheshwari book of ohopedics 6th Ed