Arthroplasty Assessment

For Medical Students

What It Tests

The assessment before a knee replacement records the deformity, the range, the stability, the function, the skin and the neurovascular state, and it checks that the knee is the source of the symptoms. 4.18.2 covers established disease.

It is a complete examination rather than a set of tests, and its purpose is a record rather than a diagnosis.

It also tests whether anything other than the knee is limiting the patient, because a replacement does not fix a hip or a spine. 4.2.15 covers referred pain.

How It Is Performed

Confirm the source: the pain is at the knee, reproduced by loading the knee, and not reproduced by moving the hip or the spine. 4.2.15 covers referred pain.

Record the function in activities, with the walking distance, the stairs, the chair and the sleep. 4.18.6 covers functional limitation.

Record the alignment standing in both planes, naming varus, valgus and fixed flexion separately. 4.3.3 covers standing alignment.

Record the range, with the extension deficit stated first. 4.5.4 covers the flexion deformity.

Record the correctability of the deformity and the state of both collateral ligaments. 4.3.10 covers the deformity.

Examine the skin for previous incisions, ulceration, cellulitis and venous change, since all affect the approach and the risk. 4.3.6 covers skin changes.

Record the neurovascular state, including the pulses and the sensation, as a baseline. 4.6.10 covers the popliteal fossa.

Examine the other knee and the hips, because the sequence of treatment depends on them. 4.1.4 covers the structured approach.

What a Positive Means

A knee with a deformity, a reduced range, an intact neurovascular state and function limited by the knee alone is the straightforward assessment.

A fixed flexion deficit tells the operation there is posterior work to do, and it is the deficit patients most often retain afterwards. 4.5.4 covers it.

Collateral laxity on the convex side records that the balance will have to be addressed as well as the alignment. 4.12.5 covers the posterior oblique ligament.

Previous incisions and poor skin change the approach and the risk, which is why the skin is examined before the joint. 4.3.6 covers skin changes.

Function limited by the hip or the spine as well as the knee predicts a partial benefit, and saying so before the operation is part of the assessment. 4.22.8 covers the use of these scores.

MRCS Level

How It Is Performed

In a viva this is the preoperative assessment station and the expected answer is ordered and complete rather than clever.

The expected points are the source confirmation, the function, the alignment in both planes, the range with the deficit first, the correctability, the collaterals, the skin, the neurovascular state, the other joints and the expectation.

Say that you would examine the hip and the spine before accepting the knee as the source. 4.2.15 covers referred pain.

Say that you would record the expectation alongside the limitation, since the mismatch predicts dissatisfaction. 4.22.8 covers the use of these scores.

Say that you would record the neurovascular findings as a baseline rather than as a diagnostic step. 4.3.9 covers it.

What a Positive Means

The reasoning expected is that the operation corrects alignment, restores a range and balances the soft tissues, so the examination records the starting point for each of those three. 4.5.1 covers the mechanical axis.

A deformity that is correctable needs less release than one that is fixed, so correctability is a soft tissue statement rather than a bony one. 4.3.10 covers it.

A preoperative extension deficit predicts a postoperative one, which is why it is recorded separately and discussed. 4.5.4 covers the flexion deformity.

Laxity on the convex side means the balance has to be achieved against a longer ligament, which is a different problem from the alignment. 4.12.5 covers the posterior oblique ligament.

How Good It Is

The assessment is reliable for the deformity, the range and the function, because all three are directly measured.

Its contribution is the complete preoperative record, which the operation plan and the consent conversation both use. 4.18.6 covers functional limitation.

It is poor at predicting the intraoperative soft tissue behaviour, which is a known limitation rather than a deficiency of technique. 4.3.10 covers the deformity.

Long leg films provide the geometry and the templating, so the examination supplies the clinical state and the films supply the plan. 4.1.6 covers that relationship.

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 assessment decides whether to replace, what to replace and in what order, and the examination contributes to all three.

Isolated compartment disease with a correctable deformity, intact ligaments and a good range is the group where a partial replacement is weighed, and the examination defines it. 4.20.7 covers that assessment.

Multiple compartment involvement, a fixed deformity or ligament deficiency moves the knee to a total replacement, and the examination is again the discriminator. 4.20.8 covers it.

Bilateral disease and coexisting hip disease set the sequence, so the other joints are examined as part of the decision rather than afterwards. 4.1.4 covers the structured approach.

Function limited by factors outside the knee is identified before the operation rather than discovered after it. 4.2.15 covers referred pain.

Where It Misleads

The commonest error is omitting the hip, since hip disease produces knee pain and a worn knee examines abnormally regardless. 4.2.15 covers referred pain.

Correctability assessed with force overstates what the operation will achieve without release. 4.3.10 covers the deformity.

Collateral laxity assessed in a stiff or deformed knee is unreliable, because the position changes the restraint being tested. 4.12.3 covers the assessment in flexion.

Function recorded without expectation produces a technically good result and a dissatisfied patient. 4.22.8 covers the use of these scores.

A normal neurovascular examination not recorded is the same as not having been done, once a postoperative question arises. 4.3.9 covers it.

Fellowship Level

Where It Misleads

At fellowship level the assessment is the basis of a plan, and its weaknesses are the plan's weaknesses.

The clinical deformity and the radiographic deformity answer different questions, and substituting one for the other loses either the soft tissue state or the geometry. 4.5.1 covers the mechanical axis.

Correctability is a continuum assessed by hand, so two examiners record different answers on the same knee and the operative plan inherits the difference. 4.3.10 covers the deformity.

A patient whose function is limited by several joints is served by a sequence rather than a single operation, and the examination has to establish the order rather than only the list. 4.1.4 covers the structured approach.

The examination cannot assess bone quality, bone loss or the extensor mechanism's competence under load, and each of those changes the implant decision. 4.3.9 covers muscle wasting.

Expectation is the finding most often recorded loosely and the one most predictive of the reported outcome, which is a mismatch worth naming. 4.22.8 covers the use of these scores.