Thanks for all the replies - great stuff. Seen physio yesterday and he says the popliteal feels tight and lumpy, but not as much as last week. I've asked should I be doing stretches or excerises and he said not to at the moment. Even when the popliteal is aching pretty bad he can still do deep tissue massage on it - but there is still that one little spot (about size of a finger nail) that is very sore/tender. Located left of centre, half an inch below the fold line of the left knee.

He has been massaging and working on the popliteal area and upper tibiofibular joint followed by "cracking" my spine as well as the pelvis. After he does this I can do Slump test with no pain, very free.

Can I also add. Last year, I took a week off work to paint the outside of my house, so I was climbing ladders, lifting and pulling and stretching all week - not a bother on the knee. I was back in work (office work at a desk) less than an hour and the pain/ache came on again. I have another session tomorrow so I'll mention this.