Paul McGrath’s Knees

Was there anything wrong with Paul McGrath’s knees?
Or did he just hate doing training?
All of the time, we accepted his pleas
That his tired old joints were complaining.

And yet, his career got longer and longer,
Defying advancing old age.
And year after year, his physique got much stronger,
As far as outsiders could gauge.

So despite those bad knees [if they really existed],
His career had tremendous longevity.
While healthier men, who with training persisted,
Played but with comparative brevity.