A hip impingement, which is actually a pinching pain in the groin, that many people say is their hip flexor. Yet, i've seen very few people in my career that i have diagnosed with hip flex or pain. I think it's more rare t than people. Everyone should be stretched on a hip flexer every single day, every workout. Its fantastic to do. And i really only believe you only need one stretch. But it's technical to do it right. The best hip stretch i know is where you take your theyl say your going to put your right ning in the ground, and the ou gont put your left foot on the ground.