Seiza and knee/ligament pressure/tightness

I started the stretch workout today, and have a question about the movements using seiza.  When I get in this position, the thing that seems to inhibit getting my glutes to my heels is not the quads, but tightness and restriction in the ligaments(?) around the knee...as if my knees just won't bend far enough to enable the full position.  Is this something that is common?  Can it get better with practice in the position?  And if so, how often should I practice for optimal improvement but avoiding injury?

Thanks!

It will get better over time Jason. Many people have issues with these upon beginning. Stick to doing the front split series once per week and consider adding in a 45-60s hold to the end of your other workouts.