Snapping your cruciate ligament is a part of ski sports. Unfortunately. For Hermann Maier, a cruciate ligament rupture is “good form for every ski racer”. What actually happens when it happens

The human knee is a complicated machine. It has three bony elements, the femur or thigh bone, the shinbone and the kneecap. They don’t lie exactly one on top of each other, which is what makes various twisting, stretching and bending movements possible.

But this means they need something else as well to hold the bones together – and these are the ligaments. The two ligaments which keep the kneecap in place are the cruciate ligaments. And they lie, as their name suggests, in a cross formation.

They are only around 38 millimetres long and it’s actually fairly amazing how often they break. Because they have a tensile resistance of 2 000 Newton, which is the equivalent of a standard five millimetre thick hemp rope. So why do they snap so often, then?

Having your feet fixed to the skis by the bindings is one of the minor reasons. And amateur skiers are also familiar with that moment when a new carving ski breaks way. The lower leg is then turned in an opposite direction from the thigh and the cruciate ligament is pinched, as it were, between the bones.

The number of cruciate ligament injuries in ski sports increased dramatically at the start of the 2000s. This had to do with the development of carving skis more than anything, experts believe. The carving skis made skiing easier for the general public, because they are more tapered and shorter than the longer skis which were used before. For the professionals, they made narrow curve radii and sloping positions possible – you can be much quicker on the curves, which greatly increases the pressure and strain on the knee joint.

And ever-newer materials, combined with increasingly harder prepared slopes, really are making Alpine ski sports faster and faster. New knee protectors can’t help, either, given the forces impacting on the knee in professional sports – nor can lines sprayed in the snow around difficult sections.

Jumps can be particularly treacherous. If a skier loses their balance, the weight of their body is shifted backwards when they land, with the foot remaining fixed tight to the skis via the boots.

So you often don’t even need to fall over to break your cruciate ligament.