I twisted my knee 3 months ago playing football?

my foot was planted and my knee twisted away from my body.i have been to physios and im waiting on an mri scan my knee gives way now and again but not much pain.there is now a lump which i can move around and is painful i have to move it when i bend my knee.physio thinks i may have dislocated my kneecap but haw does that explain the lump?thoughts please thanks.