Common Examination Pitfalls

For Medical Students

What It Tests

This page is about the examination itself rather than the knee, because most wrong conclusions in knee assessment come from how the examination was done rather than from what was found.

Five errors account for most of them, and all five are avoidable by habit rather than by skill.

Examining a tense knee. Examining only the affected side. Examining through clothing. Omitting the hip. And accepting the patient's word for a symptom whose meaning differs between patients.

Where It Misleads

A tense knee reads normal. A hamstring contracting against an anterior drawer will resist translation that a torn ligament cannot, so the test reports the muscle. The prevention is position and warmth and time rather than force.

Examining one side removes the only normal you have. Laxity varies widely between healthy people, so a figure on its own means little and a difference means a great deal.

Clothing hides wasting, scars and swelling, and all three are visual findings. Both knees exposed, every time.

Omitting the hip misses referred pain, and in a child with knee pain and a normal knee the hip is the diagnosis often enough to make it a rule rather than a courtesy. 4.19.1 covers the paediatric version.

And the symptom words mean different things to different patients. Locking, giving way and instability each have a clinical meaning and a lay meaning, and the two rarely match. Ask what happened rather than what to call it.

MRCS Level

How Good It Is

The pitfalls matter in proportion to how good the test is to begin with, and the ranking is worth holding.

For a test that is already strong, such as the Lachman, poor technique is the dominant source of error, and the usual fault is a grip that lets the femur move. 4.10.4 covers the technique.

For a test that is weak to begin with, such as the standard meniscal tests, technique matters less because the test's ceiling is low either way. The error there is over-interpreting a positive.

For a test that depends on relaxation, such as the pivot shift, patient tolerance is the limiting factor and no amount of technique overcomes guarding. That is the test most transformed by anaesthesia. 4.10.6 covers it.

Where It Misleads

At this level the errors become subtler and are mostly about what a finding is allowed to mean.

Reading a positive provocative test as a diagnosis. A positive McMurray says the manoeuvre reproduced a click or pain, and those tests are specific rather than sensitive, so a negative result changes very little. 4.9.3 covers it.

Recording a laxity grade with no endpoint. A grade describes how far and where it stopped, and a number alone cannot be compared with anybody else's examination later.

Testing at the wrong flexion angle, which converts a correct technique into a wrong finding. Valgus stress at full extension and at thirty degrees test different structures. 4.12.2 and 4.12.3 cover the two.

Performing provocative tests in the wrong order, so that each subsequent test is done on a more painful knee than the last.

And attributing an effusion. An effusion says the joint is irritated and says nothing about which structure is doing it. 4.8.2 covers the significance.

FRCS Level

How Good It Is

The structural remedy for most of these is not more skill. It is a protocol, a record and a second examination.

A protocol prevents omission, which is the dominant failure mode. 4.1.4 covers the sequence.

A record with endpoints and angles makes the second examination comparable, which is what turns a snapshot into a trajectory. 4.1.8 covers the record.

And a second examination at two to six weeks converts an acute, guarded, uninformative knee into an assessable one, which is the single highest yield intervention in this chapter and costs only an appointment.

Where It Misleads

The errors that reach a decision are different again, and they are errors of inference rather than of technique.

Concluding from a scan what only an examination could establish, which 4.1.1 treats as the commonest error in knee practice.

Accepting a previous normal examination. A recorded normal is believed downstream and rarely repeated, so an incomplete examination propagates.

Testing anterior translation and concluding about stability. Anterior laxity and rotational laxity are separate findings and a knee can have one without the other, which is why rotational instability is the commonest missed pattern. 4.14.5 covers it.

Examining too early and deciding on it. The acutely injured knee under-reports laxity because of guarding and effusion, and a reconstruction decision taken on a first examination is taken on the least informative one available.

And examining a degenerate knee as though a single structure were responsible. In that population several findings are usually present and the examination's job is to rank them rather than to select one. 4.18 covers the osteoarthritic examination.

Fellowship Level

Where It Misleads

In referred practice the pitfalls are mostly inherited rather than committed, and the skill is recognising which previous error produced the patient in front of you.

A failed cruciate reconstruction with good tunnel position and persistent rotational complaints usually means the rotational component was not examined before the first operation rather than that the operation failed.

A patient with a posterolateral injury presenting late almost always had a dial test at one flexion angle or none, which is why that test's two angle requirement is stated wherever it appears. 4.13.4 covers the test.

A patellofemoral problem treated as tibiofemoral usually follows from a scan finding that happened to be present.

And a stiff knee after reconstruction frequently traces to an examination that recorded range without recording the end feel, so a developing contracture was invisible until it was established. 4.7.5 covers end feel.

The honest limit of this page is that every claim on it is a pattern observed in teaching rather than a measured frequency, and this build cited nothing for any of them.