I had a calcified bulging disc, nerve damage down my right sciatic nerve, and really struggled to find a bike that could work with that...but didn't want a recumbent, because, as a driver, I know even I have a hard time seeing those little flags when they're out on the streets in traffic.
Anyway after working with my physical therapist, I was advised to get a mountain, rather than road bike, with really good suspension, and a really upright stance, not leaning forward at all. It was difficult finding something that felt right and worked with my short arms, and I'm just a little commuter running errands and going to work, so I'm not a super knowledgeable biker with a huge budget for upgrades. But I will say that my Trek 2700 (found at a pawn shop!) was perfect, and, frankly, felt better than driving.
There are also "nerve flossing" exercises you can do, which will make the motion of pedaling less painful. Lay on your back, hold your knee to your chest, with your hands behind your thigh, and straighten and bend your knee. This pulls the nerve through it's sheath, and actually helps alleviate pain and inflammation. Anyway, it really helped me.
And, frankly, if you had posted this in 50+ I wouldn't have seen it. I slipped my disc when I was 22, and I'm only 34 now! It's not just 50+ folks who have injuries!