sudden onset clicking knee

[emalra]

3 weeks ago i noticed that my left knee started clicking when i go upstairs or when i stand up from a seated position. It is painless with no history of injure or discomfort in the knee, i thought it will disappear by its own in few days but it is still there 3 weeks later, it does not sound like the normal popping that most joints does, it is a loud sound that i did not hear before, any suggestions? I am hoping that it will go away by itself. I am 29 years old female and am 7 weeks postpartum.