Inside of the knee could be a medial meniscus tear...again, best to see a doctor. It is impossible to diagnose you over the internet: someone needs to move your knee and feel/listen to what's happening.
Supported bridge (with cushions doing the support, not your arms) is very yin...eventually work to having legs straight.
For sciatica, again a doctor would be helpful, or a physio. In the meantime, you can read my article Sciatica and Yoga to see if there is anything helpful for you in there.
Cheers
Bernie
