Then yesterday there was this lump of ache somewhere in the fleshy muscle part on my left thigh above the back of my knee, a bit to the right, where a muscle dips to join the muscle leading to the inner thigh. At first it was just a lump of familiar ache, like I bumped it on the corner of a table. Then as the day progressed the ache changed character and it then felt like a pulled muscle or a trapped vein or even a torn bit of something. I started favoring my left leg since the pain tended to sharpen when I straighten my leg suddenly or make any sudden twists or bends at the knee. So now I'm limping a bit.
My suspicion: a belated result of going up and down the stone benches at the Kowloon Park trying to get a good shot of the flamingoes. There were a couple of particularly high benches that I climbed in a single pull and I remember a quick twinge in the same area that is aching now.