Brian,
I don't know what "grabbing" means.
Locking = the knee either won't straighten at some point or won't bend at some point, but by moving it around, it can sometimes free up.
Giving way = usually happens when quads need to activate like when you go down stairs.
Does either occur?
Just a thought...if symptoms haven't changed all that much...why not get the MRI? With your extensive history, you may just be predisposed to such injuries. At least you'll know.
Bill
P.S. Check you PM
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