I don't have enough specific knowledge about this to know what will work best, but I'm imagining maybe a swing/sling might be good- something you can still lie in, with more freedom/other places to put your legs than a bed offers.

Have you tried one of the pleasure slings to help hold your legs up in the air? You also might try a sex swing, if you're willing to make the investment; mine is wonderful for my bad back!

Numbness is usually due to a circulation issue or a nerve issue. Nerves usually result in more of a tingling numbness or pain where as circulation issues result in numbness like your foot went to sleep. The fact you say it is hard getting up tends to make me think it is a circulation problem. Most likely by putting this leg into that position (and as a result of previous injury) you probably are cutting off circulation. The mere fact your legs are in the air will make blood drain - and by cutting off supply, the blood that drains is not getting replished. Have you ever looked to see if you lose color in that leg? Have you tried having the problem leg to the side and the other leg up? Or have you tried differing levels of height - such as having the leg propped up on a pillow as oppose to up? We designed our bed height so that when I am standing I am perfectly aligned with my wife. We also position the bed so that she can have her knees bent slightly and can put her feet against the wall. It takes the pressure off of both of us from having to hold her legs up and it frees my hands to touch her. My wife has arthritis and finds this position less painful. Hope this helps.

Sorry this pain keeps happening for you. I don't know your situation, but have you seen a neurologist? My sister had an issue with a nerve in her elbow area, and the actually did surgery to relocate it so it wouldn't be irritated. Don't know if massage therapy or chiropractic could isolate the problem either. I wish you the best.