Here's the summary:
From Jan to mid April I put in some good weekly miles, averaging about 180mi, ~12,000' a week via commuting, group rides and a few event rides. Took 3 weeks off starting mid April for wedding/honeymoon (did a lot of walking on honeymoon). Get back in mid May and am sick so had to take another week off the bike.
So last day on the bike was April 21st before time off and first day back on the bike was May 20th.
Here's how things shaped up when I got back:
May 20th: 13mi, ~1000' elevation. Everything felt fine
May 21st: 21mi commuting, ~1100'. Knee ached on both rides
May 22nd: 26mi commuting, ~1600'. Knee ached a little more on both rides
May 23rd: 24mi commuting on the rain bike, ~1200'. Knee felt a bit better but still ached a bit
May 24th: No ride
May 25th: 21mi pre-event ride, ~1500'. Knee actually felt great as did the rest of my body
May 26th: 71mi event ride on rain bike, ~5000'. Knee hurt pretty bad by mile 30 or so and ached much of the rest of the ride
The pain I'm having is the front of my left knee and only reproduces on the bike. Walking and climbing stairs feels fine with no issues. My right knee has no issues at all.
Nothing has changed about my bike fit (confirmed seatpost hasn't moved on either bike, I mark them with a sharpie) and I'm wearing the same shoes as I always do and I checked the cleats and they do not appear to have moved at all.
Any ideas why just one knee would be feeling so badly and why 2 out of the 6 rides had no pain at all? Also any tips on care off the bike (ice or heat?).