Gait Observation

For Medical Students

What It Tests

Gait observation tests how the knee behaves under the load it actually carries, repeated at a cadence no manual test reproduces.

It is a screen rather than a diagnosis. An abnormal gait says the limb is compensating; which structure it is compensating for comes from the rest of the examination. 4.4.1 covers normal gait in detail.

The chapter on gait examination covers the named patterns. This page covers the observation itself: where to stand, what to look at, and in what order. 4.4.2 covers the first of those patterns.

How It Is Performed

Expose the whole limb from the hip down, including both knees, because a gait observed through trousers is a guess.

Give the patient a distance to walk in a straight line, towards you and away from you, long enough for a pattern to repeat.

Watch from the front first, looking at the knee's alignment in stance and whether it moves sideways as it takes weight. 4.5.7 covers dynamic alignment.

Watch from the side next, looking at whether the knee reaches full extension at heel strike and whether it flexes through stance.

Watch from behind last, looking at the heel and the hindfoot, because a foot that pronates changes the knee's loading. 4.5.1 covers the mechanical axis.

Ask the patient to turn at each end, and watch the turn rather than waiting for the walk back.

What a Positive Means

A shortened stance time on one side is antalgic and points at pain. 4.4.2 covers it.

A knee that moves laterally as it takes weight is a varus thrust, which points at lateral ligament deficiency or at medial compartment collapse. 4.13.4 covers the corner.

A knee that moves medially as it takes weight is a valgus thrust, which points at the medial side or at a lateral compartment problem. 4.5.3 covers valgus alignment.

A knee held in slight flexion throughout stance suggests a flexion deformity, an effusion, or a quadriceps that cannot hold extension. 4.7.8 covers extension lag.

A knee that extends fully and conspicuously early in stance, with no flexion wave, is quadriceps avoidance, and it is the gait of a cruciate deficient knee. 4.4.3 covers it.

MRCS Level

How It Is Performed

In a viva the examiner is testing whether you have a system, and front, side, behind, turn is the system.

The expected points are the exposure, the distance, the three viewpoints, the turn, and the comparison between sides.

Say that you would look at the hip and the ankle as well, because a thrust can originate above or below the knee and the gait cannot tell you which without examining both. 4.1.4 covers the structured approach.

Say that you would note the cadence and the step length, since both change before an obvious limp appears.

Say that you would record what you saw rather than a diagnosis, because the named patterns overlap and the raw observation survives better in a letter. 4.1.8 covers the record.

What a Positive Means

The reasoning expected is that the knee's stance phase has a flexion wave which absorbs load, and that most abnormal gaits are modifications of that wave. 3.14.2 covers the stance phase.

A knee that cannot tolerate the flexion wave, because of pain or quadriceps weakness, extends through stance instead, which is the mechanism behind quadriceps avoidance. 3.14.9 covers the cruciate deficient gait.

A thrust is a sudden change in alignment under load, which means a restraint is absent rather than merely stretched, and that distinction is what makes a thrust more significant than a measured laxity. 3.13.7 covers dynamic alignment.

An antalgic pattern shortens the time spent loading the painful side, which is why it is the most common abnormality and the least specific. 3.14.1 covers normal gait.

How Good It Is

Gait observation is the most informative thirty seconds of the knee examination and the least often recorded, and both halves of that are worth stating.

It is sensitive and not specific. Nearly every significant knee problem changes the gait, and the change rarely names the problem.

It is more reproducible than most people expect for the gross patterns, a thrust and an antalgic limp among them, and considerably less reproducible for the subtle ones.

Instrumented gait analysis measures what this estimates, and it is a research tool rather than a clinic one in most practice. 3.14.1 covers the underlying analysis.

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 gait observation changes two decisions, and both of them are about whether an operation will hold.

A varus thrust in a knee being considered for a lateral ligament reconstruction means the limb is loading the reconstruction with every step, and the decision moves towards correcting the alignment first. 4.13.8 covers combined injuries.

A valgus thrust in a knee being considered for a medial reconstruction raises the same question on the other side. 4.12.8 covers that assessment.

Quadriceps avoidance in a cruciate deficient knee is the gait that predicts a functional complaint, and in a patient with a grade three Lachman and no complaint its absence is part of why there is no complaint. 4.10.3 covers the chronic knee.

Post-operative gait is also where a technically successful operation shows itself as unsuccessful, and following it is more informative than following the laxity. 4.4.7 covers it.

Where It Misleads

The commonest error is not observing it.

The second is observing it through clothing.

The third is attributing a thrust to the knee without examining the hip and the ankle.

The fourth is reading an antalgic limp as a diagnosis rather than as evidence of pain, which it is and nothing more.

The fifth is recording a named pattern that the observation does not support, since the named patterns are idealisations and most real gaits are mixtures. 4.4.6 covers one of those idealisations.

Fellowship Level

Where It Misleads

In referred practice the gait is where the question behind the referral is usually answered, and it is usually the part nobody has recorded.

A patient with a stretched posterior cruciate graft and a varus thrust has the mechanical explanation for the stretch, and no laxity measurement supplies it. 4.11.2 covers the drawer.

A patient whose gait has deteriorated while the measurements have not is developing compartment change rather than ligament failure, and the gait sees it first. 4.11.6 covers that progression.

A patient with a thrust after an osteotomy has either an under corrected alignment or a ligament problem the correction exposed, and separating them needs the standing radiographs alongside the gait. 4.5.1 covers the mechanical axis.

An incompletely recovered common peroneal nerve palsy produces a gait abnormality that is permanent and is not ligamentous, and it is routinely attributed to laxity in a knee with lateral surgery. 4.13.4 covers the corner.

In an athlete the clinic gait is normal and uninformative, so the observation has to be moved onto a task that approaches the demand that fails. 4.4.9 covers single leg landing.