Hii Gayan,
Thank you for your kind words.. much appreciated
Well, coming back to your knee issues.. It looks like you have a bit of tightness in your left leg, which could be the reason of heaviness or lack of flexibility as you claim.
Do you have a tendency of folding or keeping your left leg bent from the knee / hip more than the right ?? (you would need to contemplate over this a little, coz sometimes people develop a habit of certain postures in their daily routine without realising)
In case you do, that is one aspect we can work on a few days later once there is a decent amount of improvement in your current pain.
(Legs Extension by raising each leg up) - regarding this exercise, please make one slight change while performing this i.e. whilst raising each leg, only raise it to the point that doesn't give you any kind of discomfort at low- back level whatsoever. The stretch effect you feel at the back of the thigh / calf is fine but there should be no pain in the back.
Do get back to me after about 5-6 days to discuss your condition. 
Regards,
Bellona.