Need some experience on knee pain? Can you tell me what is going on?

It’s on the left knee on the inside of the knee. I’ve good range of motion in the knee and the pain started when i reached down to get my shoes and all the weigh was on that knee. It hurts like heck. It’s not swollen and doesn’t hurt while sitting.

My doctor gave me a shot of cortisone in the area, but it still hurts. Physical therapy said, “pack in ice!” Did that…still hurting. BAD.

Anyone here have any experience with this knee problem? I really do not think it is arthritis all of a sudden like this – just out of no where. Help? Don’t even want to think about knee replacement….no!