We introduced these tummy lying backbends in class recently. There are a whole lot of things you can do with your arms in them.
This post is just for watching and not really for practicing until you come to class and I can talk to you and we can consider what is going on with your knees, spine, and shoulders and figure out what might be safe and comfortable for you.
Always remember you do not need to take your foot at all. If you have troubles with your knees, spine, or shoulders you should talk to your teacher before you even consider it. You can just bend the knee and reach towards your foot without actually taking it, as shown below. For some people this will be enough.
Some other things to consider in the variations I show in the video is the shoulder is rolling out when you take it back. It rolls in again in some variations and stays there or rolls back out again while possibly doing a variety of other things around the shoulder, shoulder blade and elbow joint complexes.
The point is, there is a lot going on around the shoulder joints and you really need to take extreme care before embarking on any of these variations.
For that reason I am just showing them here so you can maybe take a look in slow motion and have a visual memory of the movement patterns for when you come to class and we can discuss more in person.
The three shoulder variations I show in the video are shown below. In all of these positions I am basically doing the same thing with my leg, which is to press my shin or foot away and then up.

I am mindful of how the knee is feeling and I don't feel squashing in the knee joint.
I am mindful of how the shoulder is feeling and I don't feel over-stretching at the shoulder joint.

I make sure I can breathe naturally (although the breath tends to quicken here). I relax and soften my face.

Just for fun I also made this video of natarajasana on a table, which shows the same arm variations. It is more tricky because you have to balance as well.
Learning on the table beforehand helps you sort out the feeling in your spine.
Happy and safe practicing.
Much metta,
Samantha
www.yogacafecanberra.blogspot.com
www.yogacafelk.blogspot.com