I am now into week 11 since surgery and at week 5/6 the tight feeling across the front of my knee started and pretty much stopped any real progress with ROM as it was impossible to get past the pain of the stiffness when bending beyond a certain point.
It was only in week 9/10 that I noticed any change and now in week 11 I can definitely say that the stiffness is subsiding quite substantially. However, that stiffness at the front of the knee, which was ever present, has been replaced by a similar feeling at the back of the knee but only when trying to bend beyond a certain point.
Nevertheless I measure this as an improvement, which is a welcome change, as I feel I had been stuck for a few weeks without any real gains and feeling somewhat frustrated.
Hang on in there it seems that your body will let you know when it is ready to move on.