Low lunge pose has long been recommended for tight hip flexors. These are the muscles on the top of the thigh that tighten up from prolonged sitting. But overstretching in this pose can lead to hip and low back instability and pain. It is important to know the body's limits.
You know what it is: one hip pushed out to the side when standing, usually to hold a child. In the physical therapy world, it is "Hip Adduction Syndrome." Daddies can get it too, and so can non-parents, but women who are mothers are most susceptible. Over time, standing this way puts pressure on the hip and predisposes the lower back, knees, neck and shoulders to arthritis.