Functional Limitation

For Medical Students

What It Tests

Functional limitation is the measure of how much the knee interferes with the patient's life, and it is recorded in activities rather than in degrees. 4.7.9 covers the functional range.

The examination here is partly observation and partly structured questioning, because the activities that matter cannot all be performed in a clinic room.

It belongs in the examination because the treatment decision in a worn knee is made against function more than against any structural finding. 4.18.7 covers that assessment.

How It Is Performed

Ask the walking distance in units the patient uses, such as the distance to a named shop, rather than in metres they would have to estimate. 4.7.9 covers the functional range.

Ask about stairs, specifically whether they are managed one at a time and whether a rail is needed. 4.4.10 covers functional movement screening.

Ask about rising from a chair, getting in and out of a car, and whether a stick is used and when it was started.

Ask about sleep, since night pain and disturbed sleep mark a different stage from activity pain alone. 4.2.1 covers pain.

Observe the patient rising from the chair in the clinic without help, which tests quadriceps function and knee flexion together. 4.4.10 covers it.

Observe the gait over a usable distance, since a limp that appears after twenty steps is not visible in five. 4.4.1 covers normal gait.

Record what the patient has stopped doing, because the loss of an activity is the clearest single measure of progression.

What a Positive Means

A reduced walking distance with stair difficulty, chair difficulty and stick use is the pattern of established functional loss.

Night pain and disturbed sleep indicate the disease has moved past the stage where activity modification works. 4.18.2 covers established disease.

Difficulty with stairs and chairs out of proportion to walking distance suggests a patellofemoral component. 4.18.5 covers that pattern.

A good walking distance with severe radiographic change is a mismatch, and the function is what is treated.

An activity stopped recently is more informative than a long standing restriction, since it marks the direction of travel.

MRCS Level

How It Is Performed

In a viva this is the part of the arthritic knee station candidates leave out, and including it is what distinguishes a complete answer.

The expected points are the walking distance, the stairs, the chair, the car, the stick, the sleep, the observed rise and the observed gait.

Say that you would record the function before discussing treatment, since the decision is made against it. 4.18.7 covers the assessment.

Say that you would ask what the patient has stopped doing, which captures progression better than a current limit.

Say that you would ask what the patient wants to be able to do, since the expectation is part of the record. 4.22.8 covers the use of these scores.

What a Positive Means

The reasoning expected is that structural severity and functional loss correlate only loosely, so neither substitutes for the other. 4.1.6 covers that relationship.

Demand varies between patients, so the same structural state produces different limitation and the limitation is what is being treated.

Stair and chair difficulty load the patellofemoral joint and the quadriceps together, so difficulty with both points at the front or at the muscle. 3.12.3 covers patellofemoral contact pressures.

Stick use marks both pain and instability, so the reason for starting it is asked rather than assumed. 4.4.2 covers the antalgic gait.

How Good It Is

The functional record is the most reproducible part of the arthritic knee examination, because the activities are concrete.

Its contribution is the thing the treatment decision uses, which no structural measure provides. 4.18.7 covers the assessment.

It depends on the patient's report, so it is subject to the usual limits of a history and to the patient's demand.

Scored instruments formalise this record, and this repository does not contain a validated scoring system or its weighting. 4.22.7 covers that point.

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 function is the threshold, so the examination's functional record is what the threshold is tested against.

A patient with severe structural change and preserved function is managed differently from one with moderate change and lost function, and only the examination separates them. 4.18.2 covers established disease.

Night pain, stick dependence and an inability to manage stairs are the findings that most often move a decision, so each is recorded explicitly.

Expectation is recorded alongside limitation, because a mismatch between the two predicts dissatisfaction regardless of the structural result. 4.22.8 covers the use of these scores.

Function limited by something other than the knee is identified before the knee is held responsible. 4.2.15 covers referred pain.

Where It Misleads

The commonest error is accepting a walking distance without asking what stops the patient, since pain, breathlessness and balance all shorten it. 4.7.9 covers the functional range.

A patient who has adapted completely reports little limitation because they have stopped attempting the activities, which understates the loss.

Stick use is read as a measure of severity when it may be habit, advice or another joint.

Function assessed in a clinic room overstates capacity, because the distances and the surfaces are easy. 4.4.1 covers normal gait.

A patient with low demand can have severe disease and little limitation, and that is not a reason to dismiss the disease.

Fellowship Level

Where It Misleads

At fellowship level the functional record is the main input to the decision and the least standardised part of the examination.

Two patients reporting the same walking distance can have different function, because the terrain, the pace and the reason for stopping all differ and none is captured by the number. 4.7.9 covers the functional range.

Function is reported against the patient's own adapted baseline, so the report drifts as the adaptation progresses, which flattens the apparent trajectory.

The contribution of the hip, the spine, the foot and general fitness to the same limitation is not separable by the knee examination. 4.2.15 covers referred pain.

Expectation and limitation are recorded together and are different quantities, and treating the second while ignoring the first produces a technically satisfactory and clinically disappointing result. 4.22.8 covers the use of these scores.

Scored instruments reduce this to a number, and the weighting behind any such number is a methodological question this repository does not answer. 4.22.7 covers that point.