I have really weak knee joints, is there anything I can do to make them stronger and less injury prone?

Yes. Strengthen from "core to floor." work on building core strength, buttock strength, and finally quadriceps (thigh muscle) strength. A common mistake is to only focus on thigh muscle strength, but it is important to start with a strong core and buttock muscles. Also, work on stretching such as hip flexors, hamstring, and achilles (heel cord).
Strength training. The knee joint can be helped by building up the muscles that cross the joint: quads, hamstrings, calf muscles. The best way is exercise where you recruit most of the muscle (closed chain exercises) such as squats, leg press, cycling etc.