How strange that human lives – the best part of one-hundred years if we are fortunate – are shaped by the merest fragments of time. And yet so many moments go by meaning nothing, carrying utter irrelevance. And then there are others when time conspires against you in a way that seems ruthlessly pre-determined.

I had been running for 44 minutes, an easy, meandering passage that had carried me around Holyrood and finally through the car park at the rear of the Commonwealth Pool, the shortcut for those taking part in the Seven Hills of Edinburgh Race as they near Arthur’s Seat. As I approached the pavement of Dalkeith Road, I hesitated – but only in thought and not in deed: left or right, I debated. Left. I went to turn a corner, marked by a right-angled wall too high to see over. I would never reach that corner. Instead I sprawled backwards, gasping. The front wheel of the bicycle struck my right shin, then seemed to ride up my leg until the knee threw it off. The cyclist was on the ground too, his spreadeagled bike guiltily littering the pavement. ‘Sorry,’ he said, instantaneously, then over and over again, offering his hand. I sat huddled on the pavement and stopped my watch – a painfully symbolic cessation of activity.

My mind flits back to that moment in the days that follow, ruing the cruelty of time. A split-second either way, a moment, a hair’s breadth. I did not take the cyclist’s hand, but nor did I feel any resentment. He had not set out to purposely mow me down. There was nothing more sinister at work than the curse of the split-second, and so when I could have chosen self-righteousness and told him something we both knew, instead I was just sad.

The orthopaedic department at the Royal Infirmary is not an uplifting place on a Thursday afternoon. You hear patients before you see them, clunking down corridors of artificial light, wincing as they go. ‘I’ve two new feet,’ a woman in moonboots says as she shuffles by. The registrar listens to the story I have told above: the pavement-riding cyclist and the stopped watch, but also the pain that seems to boil in my shin at night, the aching tightness behind my knee. He nods and points to his computer screen.

At a glance, there is nothing untoward, and I marvel at the miracle of own body, the gleaming white of my knee framed on the screen. But there is something called the tibial spine, he explains, the top part of the tibia that extends to the anterior cruciate ligament, and that is the problem. It is no longer where it should be. I get him to write the jargon down: ‘avulsion’. He follows the term with ‘injury’ not ‘fracture’, and I spend the journey home attempting to decipher his choice of word, rather like a teenager would seek meaning from the number of kisses on a text message. According to the screen, the area is a fuzzy, tiny abnormality, the slightest of imperfections only. This time I nod and am almost rueful: is that it?

I have told him I am a hill runner and I want my knee to perform in precisely the same way it was performing in the split-second before the split-second. He does not contradict me, presses a button to book an MRI scan, and says he will see me in a fortnight.

‘No running,’ he advises. I wonder if he is being sarcastic, but the words take me back a week – almost to the very moment of that afternoon split-second on Dalkeith Road. ‘Enjoy the rest of your run,’ the cyclist had offered. I can just about laugh at the irony of his words now – and that, I suppose, is something.