Your iliopsoas, rectus femoris, and tensor fascia latae muscles are all necessary for good posture and comfortable living, so use the Thomas Test to assess your flexibility.
How to Locate, Test and Stretch the Psaos Muscle, Hip, Iliopsoas, Psoas and more
Rowing and Mobility - Part two - Hip Flexors - Rowperfect
Thomas Test Interpretation For Hip Flexibility
How to Test For Tight Hip Flexors With the Thomas Test
Figure 1 from Lumbar lordotic angle and pelvic tilt angle in the simple modified Thomas test position are easier to assess than those in the Thomas test position: A radiographic study
Hip Flexor Stretch - Thomas Test Stretch
Thomas Test, Iliopsoas Tightness
Thomas Test - Physiopedia
PXOsteopathy - Nicosia Osteopathy & Sports Injury Clinic
Measurement of Hip Flexion / Extension and Thomas Test