I have been having this pain below my patella and a tenderness on the lateral part of my left knee, and it started when I was finishing a long ride. I was pedaling when suddenly I felt a sharp pain on the lateral part of my left knee where the tenderness currently is. Now when I walk I feel a slight weakness in my knee and it becomes worse when I cycle. However, when I run, the pain almost completely subsides. I had a marathon this past weekend and was able to run the entire thing without once complaining about any pain in my knee.

This seems pretty odd to me, so I was wondering what anyone thinks this might be. Thanks!