Chiropractor to get knee/ankle/hip lined up right. That usually does it for me.
Patella strap seems to let me ride very relaxed on my tricky leg. I use it for warmup always. After 15 miles, take it off.
Make sure seat is appropriate height. 30 degree leg bend, more or less. I mostly see people too high with odd knee pain and problems. Endurance can handle a little more bend. Lower than I used to see as standard. Check out the riders in the peloton - more knee bend than I usually see in club rides. Pretty funny. I have my wife measure my knee bend to be sure I'm in a good range. Usually the bend you've been riding feels best, which skews the "by feel" adjustments.