I passed the 80% done mark of this Lands End to John O’ Groats run the week before last, fairly pleased that I seemed to be catching up on the time I’ve lost through the health problems, and my new approach of no longer wearing myself out by running for 45 minutes or an hour at a time. I was hoping that I’d reach this milestone before I left Hong Kong and it flashed past almost unnoticed.

A problem has arisen, however, because I’ve had horrible pain and stiffness in my right knee for the last four weeks, exacerbated by my insistence on three running workouts every week. Just as my knee gets some R&R, here I come, crashing back down on my joints.

The doctor says I’ve probably torn some cartilage somewhere and that it will recover with rest, glucosamine and turmeric and gentle exercise. She suggests that it might also be general wear and tear or, quel horreur, the onset of arthritis.

A wave of realisation of my own mortality crashed over me when I heard that: I have climbed that steep hill to become the fittest and healthiest I’ve probably ever been in my life and now all that faces me is a downward slope of aches and pains and stiffness and no longer being able to do stuff. I’m abject.

I hobbled around Hong Kong on Saturday afternoon, taking taxis where I would normally have walked and taken the MTR, my ankles and wrists and general posture buckling like a woman thirty years older. I was filled with the real worry that one day I’ll get up in the morning, get out of bed and collapse into a heap of mouldering bones on the floor.

Now, I’m advised to rest the knee, but on the other hand I currently have a 113 day Move streak to maintain, my longest ever, of course. In a couple of weeks I’ll have achieved four perfect months of Apple activity rings. Why would I want to break that?

So I’ve decided that I’m not going to do any running workouts this week. I’ll trundle around town and make up my Exercise and Move minutes by walking on my treadmill instead. With any luck the lower impact of walking combined with Voltaren gel and a hugely sexy elasticated knee stocking should help my knee mend.

And just because I wake in the middle of the night embedded in a nightmare of aching fingers and wrists and ankles and hips, I’ll try and get myself checked for incipient rheumatoid arthritis, if only to be able to elimate that possibility.

All of which means that it’s going to take me a little bit longer than I’d hoped to complete my run to John O’Groats. I’m hoping to reach Loch Ness before I return to Beckenham and I will complete the course, eventually.