Achilles had his heel, Harry Kane has his ankles — even the greatest have physiological limits.

Except those flaws are often what make them great.

Greek mythology tells it that Achilles, a Greek war hero, was held by the back of his foot when dipped in the River Styx, separating the lands of the living and the dead, as a child. This turned him invincible, barring the spot which carries his name, and (how’s your luck?) where he was killed after being struck there by an arrow.

Since 2016-17, ankle injuries have bedevilled Kane’s career on seven different occasions. He tore ligaments there in 2018-19, and combined has missed a full league season’s worth of games through those issues.

And yet, the same physiology that predisposes him to these ankle problems explains his world-class ball-striking and outstanding goalscoring records: the England team’s all-time top scorer, one of only three players with more than 200 Premier League goals, the best debut season (in terms of goalscoring) in Bundesliga history.

The Athletic spoke to football biomechanist Archit Navandar to understand what he calls Kane’s “floppy ankles”, and why they make him so good.

First, a lesson in physiological and biomechanics.

The human ankle is a complex thing, the point where the shin bone (tibia), calf bone (fibula) and talus (heel) meet. Scientists call it a ‘hinged synovial joint’ because movement primarily occurs in one plane (direction). In this case, up and down. The ankle can flex the foot towards the body (dorsiflexion) and extend away from it (plantarflexion) but with limited rotation. Synovial refers to the fluid in the joint, which aids movement.

“We don’t have the same ability that we have with our hands that we have with our feet,” says Navandar. “We don’t have that same dexterity. It’s very easy to rotate our wrists. An ankle, to have the same level of dexterity, you need to train. Rotation is very, very difficult, because the stiffer your ankle is, the more control you have in your kick.”

Watchers of Premier League football on UK broadcasts will know analyst Ally McCoist’s fondness of saying a player has “picked the wrong (golf) club” when they mishit a pass. The golfing analogy serves to describe how different passes (and shots) need specific amounts of power/spin and different trajectories. To change the ‘golf club’, players “change the orientation (of the foot),” says Navandar. “A small modification can completely change my surface area of contact.”

Navandar says Kane does it better and more often than most, which makes him unpredictable.

“He gets a lot of power in his kicks but with seemingly no backlift,” says Navandar. “He doesn’t bend his knees as much, it’s not a prominent knee flexion before the kick. There are kicks where there is hip extension, but it’s not prominent. What you want to do when you kick is to increase the surface area of contact to help with maximum transfer of energy from the foot to the ball, because there is going to be some energy loss.”

Here’s a comparison of Kane’s (lower) backlift to that of Manchester City’s Erling Haaland.

Navandar explains that kicking is split into “four phases”. It starts with backswing, as the leg draws away, then it cocks (the knee bends while the leg starts to move forward again). The leg accelerates towards the ball, strikes it, then follows through.

“The initial flexion before you release, it’s a whip-like motion,” when looked at from side on, says Navandar. “What Kane does, in the acceleration part, is not (be) rigid. This changes a little bit, he is able to control the movements. It happens subconsciously, automatically.”

To simplify: as Kane is swinging his leg, he changes the orientation of his ankle to hit the ball differently. Navandar likens it to a tennis player altering their serve at the final moment.

Here is an example of a side-footed Kane goal against Manchester City when he was at Tottenham Hotspur. He shapes initially to strike the ball with the laces, then opens out his foot to finish with the instep.

It is not a clean finish, with Kane striking the top of the ball so it travels down to hit the turf on its way to the net. Even so, City’s Ederson could only get fingertips to it. “These movements are very difficult to see with the naked eye,” says Navandar.

Navandar explains that most players keep the ankle locked once the leg has been pulled back to shoot (cocking). This is because stiffer ankles reduce energy loss, which adds power. Typically, as players shoot, the ankle stays with the toes pointing to the floor (plantarflexion) to maximise the surface area hitting the ball. Kane, though, will move the foot by rotating the ankle, changing his finish.

To compensate for power loss, Navandar highlights Kane’s arm on his non-kicking side, often raised as he strikes (see pictures above): “The power that he gets is mainly from extending his arm out. It’s like a spring action using the entire body.” It is a similar motion to how sprinters throw the arm of their take-off leg backwards as they fly out the blocks.

All this is a biomechanical analysis of praise that has surrounded Kane for years: he has one of the widest finishing libraries in the game, is never fussy about how he scores his goals, and can score them with either boot. “I’m comfortable with both (feet), I don’t feel like I’m losing anything,” he told UK broadcaster BT Sport in 2018.

He ranks fourth for goals in Europe’s top-four leagues since the start of the 2019-20 season. Only Haaland (164), Kylian Mbappe and Robert Lewandowski (both 135) — Kane should face the latter tonight as Bayern visit Barcelona in the Champions League — have more than his 132.

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“He has a fantastic footballing brain,” says Navandar, “but also that he’s able to adapt his game and his technique to have this sort of flexibility and mobility in the lower leg.”

Kane’s skill set is a reflection of his academy days. A late bloomer, never physically outstanding (in speed or size), with four loan spells at lower-division clubs before he broke into the Tottenham first team at age 20, he learnt to compensate.

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All 36 of Harry Kane’s Bundesliga goals this season 🎥

▶️ https://t.co/JG8Ac4ItlW#MiaSanMia pic.twitter.com/XjIHcWLESW

— FC Bayern (@FCBayernEN) May 19, 2024

Kane observed how former Spurs team-mate Jermain Defoe would take shots quickly because of the speed of Premier League defenders, and his favourite finish is across the goalkeeper after taking a touch to get the ball out in front of his feet. It is as iconic as Kane’s trademark penalty. He generates such force in those shots that he typically rolls onto his left ankle in the follow-through. “It’s part of the motion,” says Navandar.

The only constant in Kane’s career has been change, evolving as a striker and finisher. He showed against Arsenal’s David Raya in the Champions League last season that he is capable of taking penalties where he watches the goalkeeper and then goes the other way to their dive; he used to take penalties without regarding the ’keeper.

If there were any doubts about his penalty-taking after the vital miss against France late in England’s 2022 World Cup quarter-final defeat, Kane has quashed them. He has scored all 21 spot kicks since, the longest consecutive scoring streak of his career, including a hat-trick of them in Bayern’s 9-2 Champions League win against Dinamo Zagreb in September. Those three goals made him the leading English scorer in Champions League history, overtaking Wayne Rooney.

Those two floppy ankles have also brought seven Golden Boots for club and country.

(Top photo: Catherine Ivill – AMA/Getty Images)