Cutting Manoeuvres

For Medical Students

The Principle

Changing direction means stopping moving one way and starting to move another, through one foot.

The foot is fixed and the body turns over it, so the joints between them absorb the difference.

A joint that bends mainly one way is poorly placed to absorb a twist, which is the knee's whole problem here.

At the Knee

In a cut the foot plants, the body decelerates, and the knee is loaded while being turned and pushed sideways.

The knee is relatively straight at the moment of plant, which is when its ligaments are least protected by muscle.

The combination of a planted foot, a straight knee, an inward collapse and a twist is the classic cruciate injury position. 3.7.14 covers the mechanism.

Most of these injuries happen without contact with another player.

3.12.7 covers the inward collapse, which is called dynamic valgus.

What Changes It

The angle of the turn, since a sharper cut demands more.

Approach speed.

Hip and trunk control, which decide whether the knee collapses inwards. Section 8 covers the training.

Whether the turn was planned in advance or forced by someone else.

Clinical Relevance

This is where most non contact cruciate injuries happen, which is why training programmes target it. 6.1 covers the ligament.

Being able to cut is a late milestone in returning to sport, not an early one.

Training the movement reduces injury rates measurably, which is unusual in injury prevention.

Section 11 covers injury prevention.

MRCS Level

The Principle

A cut combines a large deceleration with a change in direction, so the knee sees a high anterior shear, a valgus moment and an internal rotation moment at once.

Each of those alone is tolerable. Their combination at low flexion is what exceeds the cruciate.

So the risk is a conjunction rather than a single excessive quantity, which is why single variable screening has performed poorly.

At the Knee

Peak loading occurs within the first 50 milliseconds or so after foot contact, before voluntary muscle response can contribute.

Knee flexion at contact is typically low, often under 30 degrees, and cruciate strain rises as flexion falls. 3.7.10 covers strain during activity.

Valgus and internal rotation moments peak together with anterior shear, and the anterolateral structures resist the rotational component. 3.11.4 covers the pivot shift.

Unanticipated cuts produce larger valgus and rotation moments than planned ones at the same speed, which is a neuromuscular rather than a mechanical difference.

Chapter 3.3 covers the joint angles through a cut as kinematics. 3.3.14 covers them.

What Changes It

Cut angle and approach speed, which set the magnitude.

Anticipation, which changes preparatory muscle activity and therefore the moments.

Trunk position over the plant foot, which is the largest modifiable contributor.

Hip abductor and external rotator control. 3.12.7 covers dynamic valgus.

Fatigue, surface and footwear traction, which raise the foot's resistance to rotation.

How It Is Measured

Three dimensional capture of a standardised cutting task in a laboratory, which is the reference and is anticipated by definition unless designed otherwise. 3.16.7 covers it.

Unanticipated protocols with a light or signal cue, which are more realistic and harder to standardise.

Two dimensional video scoring of frontal plane knee position, which is feasible on a pitch and correlates moderately.

Modelled ligament loading, which is inferred rather than measured. 3.16.4 covers modelling.

No measurement of cruciate load exists in a living athlete, so the injury mechanism is reconstructed from video and from models.

Clinical Relevance

Test cutting under an unanticipated cue where possible, since planned cuts underestimate the moments.

Assess trunk position over the plant foot, which is the largest modifiable contributor.

Expect a single variable screen to perform poorly, because the risk is a conjunction.

Stage cutting late in a return to sport progression. Section 8 covers the stages.

FRCS Level

At the Knee

Cutting is the most consequential movement in this chapter and the one where the mechanics are best described and least measurable.

The injury mechanism was reconstructed from broadcast video and from modelling rather than from any direct measurement, which is worth saying when the mechanism is taught as established. 3.7.14 covers it.

The 50 millisecond window matters more than any peak value: it means the ligament's protection is whatever was already active at contact, not what the athlete does about it.

That is the mechanical case for neuromuscular training, which works by changing preparatory activity rather than by producing a faster reaction.

Prevention programmes built on this reduce cruciate injury rates in trials, which is one of the stronger results in sports medicine and depends entirely on adherence. 6.1 covers the condition.

What Changes It

Anticipation, which is the difference between a laboratory task and a match.

Trunk and hip control, which is what training changes.

Fatigue, which degrades preparatory activity specifically.

Footwear and surface traction, which set how much rotation the foot resists.

Bony morphology and slope, which are fixed and set the baseline. 3.7.20 covers the interaction.

How It Is Measured

Laboratory cutting protocols, anticipated or cued, which measure a task rather than a match.

Video analysis of actual injuries, which is the only record of the real event and is uncontrolled.

Musculoskeletal modelling for ligament load, which carries the usual error chain. 3.16.4 covers it.

Field based wearables and markerless capture, which measure in the match at lower precision. 3.16.8 covers them.

The mechanism is therefore established by convergence of weak measurements rather than by a strong one, and it is still the best supported injury mechanism in the chapter.

Clinical Relevance

Prescribe neuromuscular training as a change to preparatory activity, which is what the 50 millisecond window permits.

Expect adherence rather than programme content to decide the result, and plan for it.

Test under fatigue and under an unanticipated cue, because both conditions raise the moments.

State that the mechanism rests on video and modelling rather than on direct measurement.

Take the athlete's age, physiology, comorbidities, knee demand, psychological state and their own ideas, concerns and expectations into return to sport decisions, since fear of reinjury changes cutting mechanics measurably.