Most observers regard the mental toughness that playing in the crucible of the front row after such surgery demands as the key reason for Leonard's longevity.
Prop forward Jason Leonard will equal Rory Underwood's record of 85 England appearances when he lines up against Australia on Saturday.
It will be the latest milestone in a career that mirrors the game's transformation over the past decade.
When Barking-born Leonard started his senior career as a teenager with Saracens, the game was still stubbornly amateur and Leonard himself juggled his rugby responsibilities with his job as a carpenter.
He is now enjoying a benefit year after a decade with Harlequins and is officially one of England's elite players.
He made his breakthrough just as rugby was embracing seismic changes: with pints and pies replaced by tailored training and nutrition
"Jason was the first of a new breed. He was the first of a group brought up on the training and diet regime. We started that in 1987 and when he joined in 1990, he'd already came through that with the under-21s.
"He spans an era. He came into the team before true professionalism and has benefited from it to extend his career."
His 85th cap will take him into joint fifth in the all-time appearances rankings, and he seems certain to surpass Underwood's total by playing against Argentina and South Africa in the next few weeks.
There would be a certain symmetry should Leonard set a new England record against Argentina, as his first three England matches were all against the Puma.
Ruptured
His debut came on 28 July, 1990, in Buenos Aires and he won 40 consecutive caps in a run that was only halted when he was rested for a World Cup game against Western Samoa in 1995.
His first international game in England also came against Argentina, while in 1996 he captained England and scored his only international try against the Pumas.
He is already the world's most capped prop forward, and after starting his career at loose-head he was moved across the scrum in December 1995 to tight-head.
However, Leonard's international career might well have ended before it began.
In May 1992, he had to undergo an operation to repair ruptured vertebrae in his neck.
The surgery - anterior cervical fusion - involved him having to gets a piece of bone from his hip grafted to fuse two vertebrae in his neck.
That ruled him out of action for three months, but he did not miss any England action.
Most observers regard the mental toughness that playing in the crucible of the front row after such surgery demands as the key reason for Leonard's longevity.
Leonard's fierce pride in playing for his country is another reason.
Indeed, he was famously ribbed relentlessly by his then team-mates for revealing that he had spent the day after his debut watching his England shirt spin in his mother's washing machine.
Of course, there are more concrete reasons for Leonard's endurance. Technically, his scrum skills are superb, his handling is excellent and he is a tenacious tackler.
Off the pitch, Leonard is known as a chirpy, cheeky chap and is universally popular.
Probyn said: "Jason is one of the best guys you could possibly meet. He is very social and very comic. He enjoys his life and he enjoys his rugby.
"He is a very proud man, very proud of wearing an English shirt, and every time he puts it on he gives 150%."
Probyn's place came under threat in 1995 when the then England coach Jack Rowell questioned his fitness.
Leonard, who has never missed a Five (Six) Nations Championship game since he commenced his career, adamantly refuses to look beyond the next game.
However, if he plays all this season's Tests he will have surpassed Sean Fitzpatrick's 92-cap appearance record for a forward.
There are pretenders to his position in David Flatman and Trevor Woodman, but 10 years on, Leonard is showing no signs of flagging.
When Leonard made his debut a decade ago Probyn predicted that he would get 100 caps, and he has seen little to change that opinion.
"Prop forwards tend not to mature until their late 20's and early 30's, so Jason is coming into his prime now."