We've read the articles on how important the Psoas muscle is: one of the deep core muscles responsible for flexion attaching from the lower thoracic spine, along the lumbar, through the pelvis over the front of the hip to the top of the femor (thigh bone). The Psoas is the only muscle which connects the spine to the leg.
       That said no matter what your workout routine or sport it is, it is important to keep it stretched out.  I hear anything from pain or tightness in lower backs, knees, groins, even quads and most of the time if not all the time when I teach a proper psoas stretch the pain is gone.
        Because of the all the attachments along the spine through the pelvis and to the leg it only makes sense that it's tightness can effect more parts of the body.
        Here is a diagram of a psoas stretch to do on your own.  Do not "grab the foot" as in the photo unless you are very flexible and your body is upright as the body in the pix shows, keep the back foot on the floor and most will still feel the stretch.
         IMPORTANT keep angling your pelvis and chest upward, do not lean forward, fight your pelvis tilting toward the floor.  If you tilt towards the floor you will be giving in to the "flexion" the muscle contracts to do and that is the movement you are trying to stretch ie: do the opposite.
        Give it a try, especially those with back lumbar issues try it in the morning when you get out of bed, those who sleep in fetal position are in a shortened psoas position all night and often wake up with back pain if it's already an issue, so try the stretch upon waking. Stay Healthy!