Knee

I understand knees are complicated but does anyone have any ideas what is going on with my knee? (I have had no specific trauma to the knee.) OK, so usually once or twice a day when I straighten my leg walking I get a REALLY sharp pain and it feels like my knee is going to bend backwards (although it doesn’t ). It is extremely painful, but luckily, only last a split second. The pain is in the middle of my knee towards the bottom. A few times after that I have not been able to put any weight on it, it felt like it was broken and was going to crumble. It stayed like that until the next day. This has been going on for about 6 months and the frequency of the sharp pain is increasing. It was happening about once a week to start. The weird part is that most of the time it feels fine… But it is starting to ache after riding and I wonder if one day the whole knee is just going to blow. And to add a wrench into any ideas, I had the nerve that runs between the muscles of the inner thigh cut. So the inside of my knee has no feeling. ANY help appreciated. Is this just heading for forty normal?