Krounchasana is typically done with the bottom leg in virasana, but can be done with other foundations as well, including janu sirsasana leg.
In krounchasana, I feel that the most important alignment cue to observe is that of an uplifted spine, with the muscles of the lower back and abdomen engaged to maintain a strong foundation in the pose, both for energetic as well as safety purposes.
Some of us are gifted in the hamstring flexibility department. Some of us are less so. This pose can be a challenge to the ego in that the rush to straighten the leg can compromise the spine, even to the point of injury. I recommend working with the knee bent as much as necessary to preserve a strong uplifted spine. Have patience as your hamstrings open. Connect with the feeling of your breath as you hold the pose.
Begin with one leg in virasana, inner edge of foot drawn in toward the outer hip, toes flared. Hold the opposite foot and bend your knee to pull the knee back alongside your torso. Elongate your spine, drawing your shoulders back and lifting the crown of your head upward. Pay special attention to the orientation of your pelvis, attempting to keep it neutral, meaning that the front and back of your pelvis are equidistant to the floor. The tendency will be to rock backward in the pelvis so that your front hip bones are further away from the floor than the top of your sacrum.
Keeping this alignment in your spine, pull back with your hands as you push your foot into your hands, attempting to straighten the leg. However, do this mindfully, as sometimes there will be a tendency to “pop” the leg straight, putting strain on the posterior knee and hamstring attachments. If the leg straightens, work it toward vertical and pull your forehead to your shin.
Hold the pose for 5-10 breaths, and repeat on the other side.
