I have developed an audible popping under my right knee cap occasionally when I stand up from sitting (not on my bike). It doesn't hurt but it was a little alarming because it feels like something is catching and might eventually get painful. I consulted Dr, Google and read about this noise potentially originating from meniscus tears that call for attention. I saw my orthopedist who told me not to worry about my under the knee cap popping. The meniscus tear popping (that is worrisome) will be over on the side/back by the ACL.