Picture the scene: I'm on the sofa. The telly is on (Brazilian Grand Prix), and I have the laptop on my lap. scarlatti is on Chat. To my right is a small table with a glass on it, and a bottle of Diet Coke is between the sofa and the table.
That Diet Coke is the culprit.
If the glass is full, then my elbow hurts when I pick it up. It's at its worst when the elbow is bent and both halves of the arm are in the same horizontal plane -- so that's most of the way from the table to my mouth, then.
If the glass is empty, then it doesn't hurt so much to pick it up ... but then I don't get any Diet Coke. So then I have to pick the bottle up from the floor, and the elbow hurts then. The bottle's nearly empty, so it's not so bad, but in due course I'll start on a new bottle, and it'll weigh three and a half times the weight of a full glass.
The knees hurt too, but they've decided for the time being that they're only going to hurt when I'm going downstairs. The right one, in particular, has given up on its usual popping and clicking and is developing a grating noise. The ankles hurt when I stand on them for the first time after a period of non-loadbearing. The left wrist feels like a gearbox full of gravel.
But it's the right elbow which is giving me the third degree at the moment.