Hope it turns out to be easy to sort,
@AJinNH.....really don't need any more joints to join the party! Had to look up chondromalasia....'runner's knee' sounds much more interesting than arthritis

. I have some minor oa in my knees, but put any aches and pains in them down to picking up some of the strain from the hips....however, you've jogged my memory and one knee did blow up a few months ago and I had to ice it constantly. Afterwards I paid very close attention to how I was walking....heel/toe, trying not to limp so much, and making sure my feet were pointing straight ahead, not duck-like (also when you drive, if you place your right foot between the brake and the accelerator, and swivel the heel to either pedal, that can put a torque on the knee. I suddenly realised that many years ago when I was getting a painful right knee.....since then I try to always lift my foot onto the appropriate pedal, keeping the foot in line with the knee, and I had no further problem....until the oa popped up). While I've known intellectually about biomechanics, it hasn't really sunk in until I started having skeletal/muscular problems

still, better late than never! This oa business seems to be a journey of experimenting, theorising but never quite knowing if you've cracked it

Hope your insurance allows the MRI.....hopefully it will point you in the right direction