My new theory is that I've lost some strength in my glutes and outer thighs, and that's letting my legs twist inwards, which means my knee isn't hinging on a clean line, which is why it's swollen now.
I've been putting stress under my shoulder blades for as long as I remember. A couple months back, the knot had compressed into a diamond that wouldn't shift, and every time I slept on a plane my two smallest fingers on my left hand would go numb. Clare traced these back first to my neck, then to my right shoulder where I'd lost a great deal of mobility some two years ago showing off in a pub arm wrestling. She fixed me and now my shoulders are level for the first time in all that time: when I stepped out of her house it felt like I was standing on a hill, I'd got that used to pulling one side of my body taut.
But during that two years I'd increased my fitness considerably, and lop-sidedly too it turns out. Levelling my shoulders means I'm now resolving that asymmetry all down my body in a cascade of little problems that bubble up every time I discover an imbalance. I twinged my neck for a week putting together furniture, and when I tilted left to nod at a coffee shop the pain made me put my head between my legs standing near the Angel, and I felt that kind of deep-down bone sick I've only felt before wading through a river of snow-melt so freezing to the ankles it visits your marrow.
Then this knee thing, which I brought on by running in the snow that morning. The sky was bruised and luminous, running through the flurries let me play at being a sentient super nebula charging through a galaxy of stars, and my feet - and the curbs - disappeared under the fresh white. But I should have warmed up more and taken it slower. I thought it was hamstrings and hip flexors that day: your knee is a floppy hinge held in balance by so many muscles, and if any is a little off the bend will grate and it'll swell, which is what's happened to me. One muscle at its limit already must have been finished off by the brittle morning. Stretching has helped.
But really this is the effect of no longer going to the gym and I never realised how much those squats were enabling my runs. Time to get those into the routine, build up my left leg again and get that knee problem sorted, and chase this asymmetry right out the soles of my feet; let it go to ground like a static charge.