I gave up entirely on motorcycle specific pants as the knee armor was never in the correct place and sizes were not only not available but erratic in sizing.
I now stick with 511 Tac true-fit ( yes they do ) with armor underneath them so it sits right on the joint and stays there.
http://www.511tactical.com
The moto-cross guys know a thing or two. The armor works ( I've come off on a forest track...)
That damage would have been to my knee
they are light, fit under pants and work - seconds to strap on and with my boots i'm extremely well protected but look like I'm wearing regular pants/jeans.
Instead the armor stayed on my knee and does not move if the pants move or twist.
I also wear armored shirts for hot weather and again the armor stays on the joint.
I don't wear the kidney belt....once more the armor stays on the joint. My shoulder got torn in that come off and I'm sure it was because the armor in the Joe Rocket jacket moved off the joint because the jacket was open at the collar ( 30 degrees in a rain forest ).
Since then I use the armored shirt when it's hot.
You can add hip armor as well by way of armored shorts - many are available. I'm convinced on armor that sits on the joints and stays there.