Knee strengthening

I've had some knee pain for the last few weeks. Since paying more attention to glute/hamstring stretches to ease the low back, I've noticed the hypermobility in my knees becoming more pronounced and it is time (I suspect) to pay them some proper attention. I'm careful not to over-straighten my legs, I do leg presses (loads of kg) and extensions (20kg) at the gym.

Anything else that might help?