I think mine has JUST started at age 59 and 1/2. Had plans for a 5 night week-end this coming week-end. Last Thursday, walking across the yard, POP! There went my knee. I just returned from the surgeon's office, and I'm scheduled for knee surgery this Thursday, same day we were heading out. So canceled the trip, campground, and everything. I'll need all 5 days to recover!
Turns out I tore the cartridge in my right knee. I can't even drive right now! I asked (both) doctors what caused this since it was not the result of a fall or an accident, just walking. They both said in a very diplomatic way (independent of each other) ... "Old Age"... Things just begin to fall apart! Cartlidge in the knee deterioriates (kind of like rubber .. it's soft and flexible when new, becomes hard and brittle when it's old). Oh Joy! I have SO much to look forward to in my future now! What body part is next?