Hi Ciz. Yes, I found that the big tendons behind the knee went into painful cramps when I reached the limit of my ROM, plus the regular tight band in front just below the kneecap. Seeing as it was painful, I just avoided bending too much. My wife pointed out I was walking a bit stiff legged, which I didn't realise. I was just planting my foot flat on the floor, and to keep an even keel (ie not looking drunk) I was doing the same with the other foot. I was walking in a shuffle, like the geisha ladies on platform shoes.
An earlier issue with shin splints was caused by not putting my heel on the floor first, so I already realised how important gait was.
I took the dogs for a walk in a remote place, and made sure I put my heel down first and rolled forward so all my weight went onto the big toe (that's why it's big). That makes the knee bend much more, if it doesn't, you fall over. Very quickly, my knee loosened up, but I wasn't reaching enough bend to stretch the tendons and make them hurt. So I then did the silly walk, where I made sure I kicked my heels out and up at of each step at the back, ie trying to kick my own backside. Of course I had to start gently, only kicking up until it hurt a bit. Very soon, after about 100 yards, the knee became much looser, I could kick harder, and the pain virtually disappeared.
After a long rest, it came back a bit, but after a week I never felt it any more.
I suspect the tendons and other bits just don't get any work, so they just shorten up. Evolution has developed how we should walk, so we have to try to walk how nature intended.
I wouldn't suggest this in any way whilst we are still healing, I was virtually a year out, so everything was healed and was asking for training.
It's odd that we need physios at this end of the process, but we actually only see them at the start where they are often less use than a chocolate fireguard.
Good luck, I hope it works for you as well.