Also, in some cases, strengthening the muscles around the knee cap
and/or re-balancing the strength of the muscles around your knee
, can help stabalize it.
I have what they call "bilateral patella-alta", meaning both my kneecaps sit too high up, so you can imagine how easy it is for me to dislocate them. Due to the awkward position, I can also only wear knee gaurds for a limited time or risk "Patellar compression syndrome".