My knee pops out of place every now and then should I get it looked at?

You should. Knee pops out of place every now and then is not normal, many reasons for that, one other cause beside what doctor hawley mention condition called plica, they could be seen on the mri, the answer other was comprehensive.
Knee instability. There are many causes for knee popping. Sometimes it is the knee cap or patella that is sliding in and out of its groove causing the popping. Other times it can be the entire joint opening up or shifting abnormally such as a meniscus or ligament tear. A doctor's physical exam should help provide the answer, or an MRI may be necessary. If it is the knee cap, a strength program can fix it.