The knee seems far better today with wearing the red shoes. I'm now pretty confident that a worn heel is irritating my already sore knee. I won't say that was the cause, but it's not helping it currently.
As running is off limits I went for a swim and gained a key milestone once again: 4min/100m in a 33.3m pool (of course, no drill were involved) for over 1000m. I did have to pause between lengths and went for an asymmetric approach, 5s at the deep end and 30s at the shallow. As I became tired and slowed by stroke I got more consistent and could make the pauses more symmetrical. This gave me 3:40min/100m for the last 200m. It would be really nice to be able to maintain that for 1000m. Part of it seemed psychological - other swimmers were at the lane ends and I didn't want to crowd them so set off fairly soon. Part was trying got be steady along the length.
I must try the 'catch-up' drill next time I'm in the pool as I tend to windmill and don't have as pronounced front quadrant stroke as shown here.