This is still a point of much debate (heel strike = bad) but this has been my experience too. I had pretty bad knee issues until I adjusted my form to land on my forefoot and the knee issues pretty much went away overnight. Although to be fair other issues cropped up elsewhere but none that stopped me running as much as the knee issues did.
Running puts a lot of load through your leg joints, especially on landing (up to 3x your body weight). When landing on your heel you have very little to absorb the shock except the cushioning in your shoe. Pretty much the full force of landing travels straight up your heel bone, through the ankle and up to your knee. However, landing on your fore/midfoot allows the natural shock absorption of your foot arch and achilles tendon to absorb much of the force of landing, and even to store some of this force to aid pushing off. That's my understanding of the theory anyway. There's a better explanation
here.
Merlin, for what it's worth, looking at the wear on those shoes you do appear to land quite heavily on the very back of your heel. This would suggest your foot is way out in front of you as you land, whereas it should be more or less underneath you. What worked for me was trying to hit the ground with the ball of my foot, this naturally increased my cadence and forced my foot to land underneath me.
Again, this is just what has worked for me so don't take it as gospel. I'm a very light runner (57kg) so that probably helps me out a lot too.