Meniscus or acl ?

Hi all,  I posted the other day about my knee issues so I'll just refresh. I've had acl reconstruction in my left leg 2 years ago.  Out of the blue my right leg started getting stiff and hurting.... fast forward a month later it still hurts, BADLY. I went to the dr. He confirmed he thought it was a meniscus tear. I'm not convinced that it's not both my acl and meniscus. The pain is unreal, walking is very painful it wakes me up at night in pain.  My knee gives out and buckles, very scary. The pain is mostly in the back of my knee and one spot in my calf area feels like someone is stabbing a knife in that one spot. Last night my leg, chin area and foot were swollen - at this point I just need an answer. I go in a week for an MRI...if insurance approves it, which is doubtful. 

Any help or advise ?  Thanks 

It has been so long since I tore my ACL and Meniscus.  But what I remember is the ACL caused my knee to buckle and the meniscus tear caused my knee to lock up and it was painful.  But that was heck 35 years ago and now I am recovering from a knee replacement on that same knee.  Also I have to say they did remove my meniscus (now I guess they just trim it) and I never did have my ACL replaced.  For the ACL I just made sure I did strength training on my legs at least 3 times a week, quit running marathons and it stopped buckling.