If you feel pain in the knee on the final pose, lift the torso higher and extend the thigh into the knee to ground the knee more.
Start by sitting in Virasana. Use whatever supports are needed to sit without any pain in the knees.
If you are sitting in Virasana with supports, build supports behind you as well so the pelvis and the spine will be on the same plane when you lay back. This might be a bolster and a blanket or several blankets.
Release the left leg from Virasana, placing the left foot on the floor with a bent knee. Position the right knee next to the left ankle with the right thigh parallel to the long edge of the mat.
Place the hands besides your hips and lift the hips slightly, shifting the buttocks forward. Lie back onto your supports.
Make sure the right knee stays grounded. If the right knee lifts, you need more supports behind you.
Once back and in the pose, lift the belly and extend the right thigh towards the right knee. Press the right hand into the right heel.
Hold for 3 to 9 breaths. Repeat on the left.
Alignment Points to maintain in the pose: Keep the sacrum balanced on the earth; keep the hipbones equidistant from the shoulders; and keep the right thighbone in line with the body.