Thank you for your query at DoctorSpring.com
Well the only thing that I am concerned about is that knees are not anatomically supposed to pop in an out of place whenever you bend them. This is because structurally speaking, the knee joint is held in proper position by ligaments and menisci. I understand that there was no severe trauma, bruising, swelling or redness or difficulty using the knee. Considering your young age, and the fact that you exercise daily, I would advise you to get an MRI just to make sure there are no ligament or meniscal tears/sprain or joint dislocations.
Hope this helps, feel free to discuss further