A popping knee without any other symptoms is generally harmless. It is caused by the rubbing together of the meniscus, which ahve been subjected to some wear and tear. There would be some slight inflammation of these, which has given rise to the popping. The only thing that you need to do now is to monitor your knee. Try to see if you have any pain or instability in the knee. The popping should go away in a week or two. If it persists beyond 20 days, or if there are other symptoms, then you need to appraoch a doctor. During this period, you also should not strain the knee, do not lift heavy weights and try to avoid any strenuous activity like walking too far, etc. You can also tie a stretchable crepe bandage or a 'knee sock' around your knee to give it some rest. In general, most such episodes are temporary and you can expect yours too to go away. You can look up here: http://diet.ivillage.com/workouts/wsafety/0,,849w9fc4,00.html I hope this answer was helpful. If you need more information, feel free to ask. For accepting this answer, please click on the green 'accept' button below. Feedback/Bonus will be warmly appreciated.