My knees pop out of place very easily. ex if i get on all fours with too much weight, laying prone, something bumping into them, why?

Knee Instability: How long did you have this problem ? Did you have any injury ? Is it one sided ? It could be dislocating patella which happens due to misalignment or it could be due to rupture or deficiency of cruciate or collateral ligaments of the knee. A meniscal tear can also lead to feeling of popping of the knee or locking. You may need MRI scan to diagnose the later conditions.

Many reasons: Most likely it is your kneecap that is popping out of place. This can be from previous trauma, general looseness of all of your ligaments, a shallow groove that your kneecap tracks in, or malalignment of your limbs. See an md to help figure out the cause of the problem.