I just turned 60 years old. I have always been active, was a basketball player as a young man, playe d;lots of tennis until 40 s, now golf, running, stationery bike, etc. Recently had sudden onset pain in left knee. Started behind the knee, eventually all over knee and upper thigh. Cannot run. Wearing a sock brace, can elliptical, bike, walk. Lots of soreness and stiffness. Xrays negative for anything other than normal arthritic changes. Now lots of aches and pains in both knees, legs, also some degree of stiffness and soreness in shoulders and lower back (no known injury). Is this just sudden onset of arthritis? Is this normal (I feel like I went from physically fit to broken down in 6 weeks).