Potassium content symptoms and conditions

I was given 20 mg of Prednisone for 10 days for a rash and joint pain.
The pain went away and I felt great the rash got a little better. Two days ago I took my last pill. I woke up that night and my knees gave out. By morning I was great! Next night I woke with knee problem again had to slide down the stairs to the living room. I got to wondering if the knee thing could be associated with the Prednisone. I got on line and read all this terrible stuff. I am so Horrified! Today I am in pain like my body is bruised and my face is swollen a little. I have acid reflux as well. Non of this is typical for me. My knee thing is ok again, but I am just appalled! I have no MED insurance. I hope this isn't the beginning of worse things I am not taking that drug now. The Dr. didn't say I needed to taper...

I hope I have not damaged myself by taking this drug! My heart goes out to all of you! My question is - Why are the Dr.'s prescribing this terrible drug?