This pose is similar to seated forward fold, and provides the same benefits. It also stretches your groin. Assume the same starting position as the forward fold, but slide the sole of your left foot against your right inner thigh. Keeping your right foot flexed, lower your left knee as far as you can into a half-butterfly position. Walk your hands down the sides of your right leg as you fold forward as far as you can with your torso. Hold for 8-10 breaths, and then slowly rise back up. Switch legs and repeat.
In order to treat this hip and leg pain, it is important to understand the causes of lower back pain. Amongst people below the age of 60, the most common cause of sciatica is a slipped or herniated disc, in the lower lumbar region of the spine. When a disc is swollen or has moved, it puts pressure on the sciatic nerve, causing discomfort and pain. This tends not to happen instantly, but instead generally develops over time. Other causes include:
Progress to add core engagement. Once they can master the posterior pelvic tilt, I usually progress to assist by curing core engagement. You can do this by pacing both hands together on top of your front knee and push straight down, or by holding a massage stick or dowel in front of you and pushing down into the ground. Key here is to have arms straight and to push down with you core, not your triceps.