Post-operative Range Assessment

For Medical Students

What It Tests

Measuring the range after a knee operation tests whether the knee is on a trajectory towards a normal range or towards a stiff one.

The point of measuring early and repeatedly is that a stiffening knee is treatable early and much harder later, so the assessment exists to allow intervention rather than to document an outcome. 4.7.7 covers contractures.

Both ranges are measured, because the active and passive figures diverging is itself the common early finding. 4.7.8 covers extension lag.

How It Is Performed

Measure the active and the passive extension and flexion at every visit, using the same method, and record all four figures. 4.1.8 covers the record.

Note the end feel at each limit, since the character of the resistance is what will distinguish the causes if the range stalls. 4.7.5 covers end feel.

Compare with the figures from the previous visit rather than with a population normal, because the trajectory is the finding.

Assess the effusion, since an effusion limits the range and inhibits the quadriceps and resolves. 4.6.3 covers the effusion assessment.

Watch the patient walk, because the gait reflects the usable range and lags behind the measured one. 4.4.7 covers post-operative gait.

What a Positive Means

A range improving at each visit is a normal trajectory and needs nothing but continued rehabilitation.

A range that has stopped improving is a stalled trajectory, and it needs a cause rather than more time. 4.7.5 covers the end feel that finds one.

A loss of extension first is the commonest early pattern, because terminal extension is the hardest part to maintain and the quadriceps is inhibited. 4.7.8 covers it.

A firm abrupt block in extension indicates an impinging lesion, which has a reliable arthroscopic answer and is the diagnosis worth finding. 4.7.5 covers it.

A global leathery restriction in both directions indicates arthrofibrosis, and the outcome is less certain, which changes what the patient is told. 4.7.7 covers contractures.

MRCS Level

How It Is Performed

In a viva this is the answer to how you would follow up a reconstruction, and the trajectory rather than the figure is the mark.

The expected points are all four measurements with a stated method, the end feel, the comparison with the previous visit, the effusion, and the gait.

Say that you would act on a stalled range rather than observe it, and say what you would do.

Say that you would relate the figures to the rehabilitation stage rather than to the weeks since surgery, since programmes differ. 4.2.34 covers previous rehabilitation.

Say that an extension deficit matters more than a flexion deficit of the same size, because it alters gait at every step. 4.4.1 covers normal gait.

What a Positive Means

The reasoning expected is that soft tissue adapts to the position a joint is held in, so a knee that has not regained extension early shortens its posterior structures and the deficit becomes structural. 4.7.7 covers contractures.

Pain and effusion inhibit the quadriceps, which produces an active deficit before any structural change, and that is why the active and passive figures diverge first. 4.8.2 covers inhibition.

An impinging lesion in the notch produces a firm abrupt block, which is why the end feel rather than the angle identifies it. 4.7.5 covers the end feel.

Arthrofibrosis involves the whole capsule, which is why it limits flexion and extension together and why the pattern of loss is diagnostic. 4.7.7 covers it.

How Good It Is

Serial range measurement is the most reliable and most useful post-operative assessment available, and it depends entirely on the method being consistent.

Its value is in the series rather than the single figure, which makes the first post-operative measurement the most important one. 4.1.8 covers the record.

The end feel adds the diagnosis and is the least reproducible element, which is the recurring trade off in this chapter. 4.7.5 covers it.

It does not measure function, which the gait and the patient's account do, and all three are recorded because they recover at different rates. 4.4.7 covers the gait.

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 post-operative range decides when to intervene, and the window is narrow enough that the decision has to be made on a trajectory rather than on a figure.

A knee that has stopped improving at six weeks needs a cause established, and waiting until three months to act is the error that produces the referrals in this area. 4.7.5 covers the end feel.

A firm abrupt block in a reconstructed knee is an impinging lesion with a reliable arthroscopic answer, and finding it early is worth the examination. 4.7.5 covers it.

A global restriction is arthrofibrosis, and an early manipulation or release has a better result than a late one, so the diagnosis changes the timing as well as the operation. 4.7.7 covers contractures.

An extension lag with a full passive range is a rehabilitation problem, and the answer is a programme rather than an operation. 4.7.8 covers it.

Where It Misleads

The commonest error is recording one figure rather than four.

The second is comparing with a population normal rather than with the previous visit.

The third is observing a stalled range rather than investigating it.

The fourth is reading a limited range in an effused knee as stiffness. 4.8.2 covers it.

The fifth is omitting the end feel, which is the element that would have named the cause. 4.7.5 covers it.

Fellowship Level

Where It Misleads

In referred practice the stiff knee after surgery arrives late, and the lateness is almost always a monitoring failure rather than a surgical one.

A patient with a firm abrupt extension block referred at a year has had a treatable lesion for most of that year, and the pattern is that the range was recorded without an end feel. 4.7.5 covers it.

A patient with arthrofibrosis referred late has a worse prognosis than the same patient referred at two months, which makes the monitoring interval a clinical decision rather than an administrative one. 4.7.7 covers contractures.

A patient whose pre-operative range was never recorded cannot be assessed for loss, and that is the commonest reason these referrals cannot be resolved. 4.1.8 covers the record.

A patient with a persisting extension lag and a full passive range has a rehabilitation problem, and further surgery makes it worse, which is a conversation rather than a procedure. 4.7.8 covers it.

In medicolegal work a stiff knee with no recorded early ranges is unassessable in both directions, and saying so plainly is more useful than inferring a trajectory that was never measured. 4.23.7 covers that setting.