I Am 71 Yrs. Old, Female, And Have Never Had

I am 71 yrs. old, female, and have never had much trouble with either knee, but now I'm having pain and "clicking" in my right knee cap area. On the inner side of my right knee, there is also tenderness to the touch and soreness in the upper back of that knee. I do not remember injuring myself, but it is causing a steady pain when I walk and there is a reluctance to bend my knee. I've used ice on it for the past day or two. Sometiems, there is an ache in the front of that leg from the patella down... Any ideas what it could be?
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