I sometimes experience a bit of knee pain on my right leg (flat footed) but its just usually when the knee has a lot of load, E.G, doing a pistol squad, when the knee is fully locked on the bottom part and i try to go up it hurts., is this related to my flat foot??
Where exactly does the pain originate and does your knee collapse inward during the pistol squat? My left leg collapses inward slightly when doing pistols above bodyweight.
Are you working on developing an arch?
For osgood schlatter have you watched either of the episodes that address it?
Pro Episode #20 Dealing with that horror show bump on your knee/osgood schlatter