So a bit of background...
I used to play ice hockey as a goalie in college, and ultimately quit due to chronic injuries that plagued mostly my knees. I mainly had issue with an ACL/PCL in my left knee which has been resolved with subsequent surgeries. I had an MCL tear in my right knee which required no surgery, and healed over time. I was able to return to the game after each injury, and after college continued to play recreationally without any problems. Over the last year I have become busy with work and have not been as active.
Last week I ran a 5K. I didn't overexert myself by any degree, but ran, jogged and walked during the span of the 5 kilometers. I have developed a "popping" or "cracking" sensation in my right knee since then. It is not painful by any means, just uncomfortable. It doesn't do it every single step, but is fairly consistent when I walk. What could be going on in my knee?
It's important to add, though my level of physical activity isn't what it used to be, I am active as a scuba instructor, and dive atleast once a week (though different type of exercise).