Last summer/fall I trained for a 50k, and towards the peak of training, I would get slight popping sensation behind the left knee when going uphill/stairs, when my left leg was the leg lifting me. After the race I took it easy for a bit with low mileage and it seemed to go away. Recently, when running up a hill in the first 1/2 mile of my run, I felt some popping, but I kept running since I was used it, even though it hadn't been an issue. However, afterwards my calf was sore. I've kept the running to a minimum in the 2 weeks since, but now when I run, particularly on gravel or uneven surface (and especially up hill) my calf has a noticeable and uncomfortable (but not painful) popping with each left step. I also feel it when standing up and straightening the left leg or walking up stairs. Is this just a calf strain that needs rest? It doesn't pop when walking normally, and there's no pain. What can I do to expedite the healing? Thanks very much for your help!