How the Idea of 'Sunk Cost' Relates to Recovering From Knee Pain

I was thinking of the idea of "sunk cost" a few days ago while trying to fix the vent for my dryer.

The vent is a four-inch wide tube, made of thin metal, through which the dryer's hot air whooshes outside. Ours is old (like everything in this old house) and I had to replace the cracked cover. Among other things, the cover keeps small animals (and insects) from entering your house through the vent.

I bought a replacement cover at Home Depot for five or six bucks. But when I got home, I immediately noticed problems: It wouldn't fit over the existing, slightly crumpled end of the vent. Also, the screw holes to hold the cover in place weren't aligned with the existing holes.

I started thinking about how I'd have to drill new holes through the siding and into the house. I'd have to get a smaller vent pipe, that would fit my new cover. I went to a hardware store in that frame of mind ... and then ...

Voila! There was a vent tube for sale with an already attached cover. At first I passed it by -- after all, I already had a cover. But then I realized: No, wait a minute. This might be exactly what I need. So I bought it, took it home, and it fit just about perfectly, no new holes needing to be drilled.

The vent cover I had just bought? I realized it was a "sunk cost" (I couldn't really return it by then, because it had been scratched up after my attempts to jam it onto the existing vent). I had to write it off and move on.

Swallowing a sunk cost can be very, very hard to do. It's in human nature not to want to give up on something that we're invested in. I know five or six bucks isn't much at all, but my thinking had completely swung around to, "How do I make this work because I've already bought it?"

Similarly, with knee pain, if you're experimenting with ways to heal, you will sometimes have to accept the harsh reality of a sunk cost. As readers of my book know, I followed a very structured plan to get better.

But sometimes that plan just wasn't working, for whatever reason.

In the book, I described going to Tibet, doing some very slow walking with my wife (fiancee at the time), and feeling like my knees had been reborn. I was getting better! So when I returned to Hong Kong, I vowed to strengthen my leg muscles, as my physical therapist had been urging, to make sure my knee pain didn't come back.

But instead of the gym exercises pushing me beyond knee pain, they pushed me back into knee pain. My old problems returned. I stubbornly persisted with the exercises until it became impossible to ignore: they were hurting me. I couldn't continue that way.

In essence, I was staring at a sunk cost of sorts. I had invested heavily in this "strengthen your quads" approach. I was religiously going to the gym, lifting leg weights, trying to get stronger. Meanwhile, my knees were getting worse. To continue doing the same thing would be insanity.

I did walk away from that approach, but it was hard. It felt like I was giving up in a way. I had sunk my time and faith into something that didn't work. It's difficult to accept that, first of all, then summon the strength to move on.

Still, there will be moments in the journey to recover from knee pain where I think we do have to write off an approach, a belief, or whatever -- as a "sunk cost." We invested in it, sometimes to an extreme degree. But if it's not paying dividends, then the smart thing to do: go ahead and write it off and accept the loss (of money, time, or whatever).

Then find a new way forward.