It's a poor term but it's talking about a healthy baseline for any human as far as I'm aware. It's not adjusted for expected deterioration due to age. 100% of organs eventually fail if given enough time, but it's still fine to call the resulting failed organ a defect.

Presumably, some of this is just it's pretty damn inevitable you're going to accumulate at least some level of detectable injury that doesn't completely heal over the course of 40 years. I needed shoulder reconstruction because I fell off a skateboard trying to bomb a hill a year and a half ago and it's healed to the point there isn't any functional impairment, but given there's metal in there now, it's obviously going to look abnormal on an image. There's just an impedance mismatch here between what imaging finds and what people actually care about. Any detectable deviation from expected tissue configuration is going to show up and get reported, but there is no reason for a patient to give a shit. Functional impairment and/or pain is what they care about, though those are both also universal if you live long enough. No 90 year-old walks without a limp but it's still completely fair to call a limp an "abnormal" gait.