I highly recommend a wedge pillow!
It makes elevation so easy, plus it's more firm which is great for
-helping to keep the leg from kinda swaying over to the left or right (rather than the kneecap facing straight up to the ceiling)
-straightening! The no "pillow behind knee" thing doesn't apply here, because it's firm and angled it doesn't allow the knee to bend versus a soft pillow does. It's essentially like just having your leg straight on the couch or bed but it's angled.
Bed Wedge Pillows, Leg Elevation Pillow https://www.amazon.com/dp/B08Q3V1ZYG/ref=cm_sw_r_apan_i_NPWZENE2B8N287ZQX41N
No problem this is the one I got. It’s pretty firm so I put my normal pillow on top, and if I’m having trouble sitting up you can rotate it and it helps support my back while sitting.
This has worked wonders for me
I needed better neck support when using the wedge and this helps immensely
https://www.amazon.com/gp/product/B07J63KGNN/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1