Urdva Prasaritha Eka Pada Uttasana it is the third position in the Prana Vashya Yoga™ sun salutation. Urdva Prasaritha Eka Pada Uttasana is a bit of mouthful to pronounce (!) and translates as "upward-split-one-leg-stretch-position".
Starting, then, from the forward bend pose Hasta Pada Asana, you should inhale and slowly lift the left leg parallel to the floor and in line with the hip, keeping your vision fixed on a single point on the floor throughout. Do NOT collapse the hip or else you will strain your knee. Put another way: your raised leg and hip will tend to externally rotate slightly which causes the pelvis to come to the right and forces the hips out of alignment/ to collapse. This often happens when you try too hard. The idea of the posture is NOT to raise your leg as high as you possibly can; keep your leg raised in line with the hip and the knee straight (not bend the knee to gain extra height!)
Pay close attention to the standing leg, keeping your knees facing forward and not letting them turn out to either side. As your leg raises higher, your torso should act as a counterbalance and come towards the floor.
Benefits
Promotes better liver and kidney function
Works the ankles, knees, calf muscles, hamstrings and thighs
Contraindications
Avoid this asana if you have any issues with your lower back, ankle(s), or knee(s).