Skiing

For Patients

The Principle

A long lever turns a small force into a large turning effect.

If something is strapped to a long lever, the forces reaching it are multiplied.

That is how a slow, undramatic fall can injure a knee badly.

At the Knee

A ski is roughly a metre and a half long and is fixed firmly to the boot, which is fixed firmly to the lower leg.

Anything that catches the tip or the tail of the ski twists the whole leg, and the knee is the first joint that can give.

Bindings release at high forces, and they are not designed to protect against every slow twisting fall.

The classic mechanism is sitting back while the ski turns away, which loads the ligament inside the knee without any speed at all.

Clinical Relevance

A knee injury from a slow fall in skiing can be as serious as one from a fast crash.

Swelling within a few hours of a skiing fall is a reason to be assessed before flying home.

Bindings should be set for the skier rather than left at a default. A shop can do this.

No injury rates are given on this page, because no source was available to check them against.

For Medical Students

The Principle

Equipment that extends a limb changes the mechanics of every injury mechanism acting through it.

A ski lengthens the moment arm in the transverse and coronal planes and stiffens the sagittal connection through the boot.

So skiing injuries are not simply high speed versions of other sports' injuries. The mechanism itself differs. 3.4.4 covers lever arms.

At the Knee

The phantom foot mechanism occurs with the skier sitting back, the uphill ski turning away, producing internal rotation of a flexed knee with valgus. It injures the anterior cruciate. 6.1 covers the ligament.

The boot induced mechanism occurs when a backward landing drives the boot's rear cuff into the calf, pushing the tibia forward. It also injures the anterior cruciate.

Catching an inside edge produces valgus with external rotation and loads the medial collateral complex. 3.9.1 covers valgus stability.

The stiff boot prevents ankle absorption, so energy passes to the knee rather than being shared. 3.4.8 covers energy absorption.

Speed is not required for any of these. Many occur at low velocity.

What Changes It

Binding settings, which govern release and are set from weight, height, age and ability.

Boot stiffness and height, which determine how much is transmitted to the knee.

Technique and fatigue, particularly sitting back late in a day.

Snow conditions, which alter edge grip and therefore torque.

Previous injury and the use of a functional brace.

Clinical Relevance

Ask about the mechanism in detail, since skiing has named mechanisms that predict the structure.

Do not take low speed as reassurance, because the common mechanisms are slow.

Ask whether the bindings released, which is relevant to the energy involved.

Avoid quoting injury rates, which this page does not, because no source was available.

MRCS Level

The Principle

Skiing is the one sport in this chapter where a technological change measurably moved the injury pattern, and it moved it to the knee.

Modern boots and bindings nearly eliminated the tibial fractures that characterised the sport decades ago.

The energy did not disappear. It moved up to the next available structure, which is why the knee is now the characteristic skiing injury.

At the Knee

The phantom foot position combines flexion beyond 90 degrees, internal tibial rotation and valgus, which is an efficient anterior cruciate loading configuration. 3.7.14 covers the mechanisms.

The boot induced anterior drawer mechanism loads the cruciate directly through the rear cuff without any rotation.

Medial collateral injury from edge catching is commoner than cruciate injury and is often managed non operatively. 3.9 covers the medial side.

Multiligament and tibial plateau injuries occur in high energy collisions, which are a different population from the recreational twisting fall.

The anterolateral structures are loaded by the rotational component and are relevant to the residual instability some skiers report. 3.11.4 covers the pivot shift.

What Changes It

Binding release settings, which are the main engineered protection and are frequently set too high.

Boot cuff height and stiffness, which determine the boot induced mechanism's availability.

Skier ability and fatigue, since the phantom foot position is a late in the day position.

Terrain and snow conditions.

Equipment hire practice, where settings are often standardised rather than individualised.

How It Is Measured

Video and witness reconstruction of real falls, which is how the named mechanisms were described.

Cadaveric and robotic simulation of the phantom foot and boot induced positions. 3.16.2 covers robotic testing.

Binding release testing to standards, which is mechanical and excludes the skier.

Resort injury surveillance, which gives rates this page does not quote, because no source was retrieved.

The shift from tibial fracture to knee injury is a historical observation in the surveillance literature rather than something measured prospectively.

Clinical Relevance

Take mechanism in detail, since skiing's named mechanisms map onto structures better than most sports' histories do.

Ask about binding release and settings, which bears on energy and on prevention advice.

Treat a low energy mechanism as capable of producing a complete cruciate rupture.

State that the historical shift from tibia to knee is an observation rather than a prospective finding.

Weigh the skier's age, physiology, comorbidities, knee demand, psychological state and their own ideas, concerns and expectations, since this is often a holiday injury in a patient whose sport is occasional.