Quadriceps Avoidance Gait

For Medical Students

What It Tests

Quadriceps avoidance is a gait in which the knee reduces or abolishes the small flexion wave of early stance, so the quadriceps is not asked to control a flexing knee under load.

It is the characteristic gait of an anterior cruciate deficient knee, because the quadriceps pulls the tibia forwards and in a cruciate deficient knee that pull is unopposed. 3.14.9 covers the biomechanics.

Recognising it matters because it is a compensation rather than a deficit: a knee doing this is coping, and the patients who cannot do it are the ones who complain. 4.10.3 covers the chronic knee.

How It Is Performed

Watch the patient walk from the side, at knee level, over a distance long enough for the pattern to repeat.

Look at the knee immediately after heel strike, which is where the flexion wave belongs, and note whether it is present, reduced, or absent.

Compare with the other side in the same view, since the size of a normal wave varies between people. 4.4.1 covers the normal pattern.

Note whether the knee is held in full extension through early stance, which is the extreme form.

Watch the patient descend a step or a slope if the walking gait is equivocal, because descent demands more of the same control. 4.4.9 covers single leg landing.

What a Positive Means

An absent or reduced flexion wave on one side indicates that the knee is avoiding quadriceps loading in early stance.

In a knee with a positive Lachman test this is the expected compensation, and its presence suggests the knee is managing. 4.10.4 covers the Lachman test.

In a knee with a positive Lachman test and no avoidance pattern, the knee has not adapted, and those are the patients who describe giving way. 4.2.6 covers giving way.

An avoidance pattern can also follow pain or quadriceps weakness without any ligament deficiency, so the pattern is not specific to the cruciate. 4.3.9 covers wasting.

The pattern is not a target for treatment. Rehabilitation aims at the quadriceps, and the gait follows. 4.11.5 covers the functional assessment.

MRCS Level

How It Is Performed

In a viva this is the gait to name when asked what you would see in a chronic anterior cruciate deficient knee, and explaining the mechanism is the mark.

The expected points are the side view at knee level, the flexion wave immediately after heel strike, the comparison, and the descent task if the walk is equivocal.

Say why the quadriceps is the problem, because the mechanism is the question. 3.14.9 covers it.

Say that the pattern is a compensation and that its presence is reassuring rather than alarming, which is counterintuitive and is what the examiner is testing.

Say that you would assess the quadriceps bulk and strength, since the compensation depends on the muscle being able to hold the knee extended. 4.7.1 covers active motion.

What a Positive Means

The reasoning expected is that the quadriceps acts through the patellar tendon, whose line of pull is anterior to the tibia in early flexion, so contracting it in a flexed loaded knee translates the tibia forwards. 4.11.3 covers the test built on the same geometry.

An intact anterior cruciate resists that translation. Without it, the translation occurs, and the knee avoids the position in which it occurs. 3.11.5 covers internal rotation control.

The same geometry means the avoidance is specific to early stance, where the knee is flexing under load, and not to the whole cycle. 3.14.2 covers the stance phase.

The pattern also increases hamstring activity, which is a second compensation and part of why quadriceps strength alone does not predict function. 4.11.5 covers that assessment.

How Good It Is

The avoidance pattern is specific for a problem with quadriceps loading and not specific to the cruciate, so it localises to a mechanism rather than to a structure.

It is reliably seen in its extreme form and easily missed when the wave is merely reduced, which is most cases.

Instrumented gait analysis detects it far more sensitively than the eye, and this is one of the clearest examples in the chapter where the measurement is genuinely better than the observation. 3.14.1 covers the analysis.

Its clinical value is as an indicator of compensation rather than as a diagnostic test, which is a real use and a modest one. 4.10.3 covers the knee it applies to.

No figures appear for any accuracy comparison on this page, under decision 023, and the comparison is the claim being made.

FRCS Level

How Good It Is

At decision level the pattern contributes to the question that matters most in a cruciate deficient knee: whether this patient is coping.

A patient with a grade three Lachman, an established avoidance pattern, a strong quadriceps and no complaint is a patient who has adapted, and the laxity is not an indication. 4.10.3 covers the chronic knee.

A patient with the same laxity, no avoidance pattern and a complaint of giving way has not adapted, and that is the patient reconstruction helps. 4.2.6 covers giving way.

Post-operatively the pattern's persistence is a measure of incomplete rehabilitation rather than of graft failure, and it resolves with quadriceps work rather than with surgery. 4.4.7 covers post-operative gait.

The pattern also has a cost. A knee walking without a flexion wave transmits load differently, which is part of the argument about long term compartment change in the deficient knee. 3.14.9 covers that gait.

Where It Misleads

The commonest error is looking for it in a walking gait only, where a reduced wave is hard to see.

The second is reading it as a sign of a worse knee, when it is a sign of a compensating one.

The third is attributing it to the cruciate without considering pain or quadriceps weakness, both of which produce it.

The fourth is treating the gait rather than the quadriceps, which is treating the compensation and not the cause.

The fifth is expecting it to resolve immediately after reconstruction, which it does not. 4.4.7 covers that timeline.

Fellowship Level

Where It Misleads

In referred practice the pattern's presence or absence often explains a disagreement between the measurements and the patient.

A patient with a competent reconstruction and a persisting avoidance pattern has a quadriceps that has not recovered, and that is the commonest reason a technically successful reconstruction disappoints. 4.3.9 covers wasting.

A patient who has lost a previously established avoidance pattern and is now limping has developed pain or compartment change, and the gait has changed category rather than degree. 4.4.6 covers the arthritic gait.

An athlete can walk with a perfect flexion wave and still avoid quadriceps loading at the intensity that fails, which is why the assessment has to move to the sport's demand. 4.4.8 covers running gait.

In a knee with a lateral extra-articular procedure the rotational control is altered, so the gait adaptation may persist for mechanical reasons unrelated to the quadriceps. 3.11.7 covers the procedure.

In a posterior cruciate deficient knee the mirror pattern appears, because there the quadriceps is the compensation rather than the problem, and reading the two chapters together is what makes the mechanism clear. 4.4.4 covers it.