This is the flow Dan Castle does every morning to start his day and its how he fixed his herniated disc (L4 L5) issues.

Its NORMAL to not be able to rest your leg knee straight onto the surface at 0 degrees when starting the pendalum stretch. You may only be able to start at 30 degrees but over time you will release the tightness in your hammies and calves and one day you will notice that your leg is fully extended and resting on the floor! Thats the goal.

Do this flow daily.