Valgus OA

For Medical Students

What It Tests

A valgus knee with lateral compartment wear presents as lateral joint line pain, a knock kneed appearance worse on standing, and sometimes a feeling of the knee giving way medially. 4.5.3 covers valgus alignment.

The examination is deciding the size of the deformity, whether it corrects, and whether the medial side has stretched. 4.3.10 covers the deformity.

It matters that this is the less common pattern, because a valgus knee raises the possibility of an inflammatory or a post traumatic cause rather than simple wear. 4.8.9 covers synovitis.

How It Is Performed

Take the history: the lateral pain, the duration, whether there was a previous fracture or a previous lateral meniscectomy, and any inflammatory features. 4.2.9 covers the onset.

Look at the patient standing from the front with the knees together, because the deformity is loaded. 4.3.3 covers standing alignment.

Watch the gait from the front for the knee moving medially during stance, which is the medial thrust. 4.4.6 covers the arthritic gait.

Palpate the lateral joint line in flexion for tenderness and osteophyte. 4.6.4 covers joint line tenderness.

Assess correctability with a varus force near extension, recording how much the alignment improves. 4.13.2 covers the lateral collateral assessment.

Assess the medial collateral ligament, since a long standing valgus knee stretches the medial structures. 4.12.1 covers valgus stress testing.

Measure the range and record any fixed flexion separately, and look for an external rotation deformity, which accompanies valgus wear. 4.5.4 covers the flexion deformity.

What a Positive Means

Lateral joint line tenderness with a standing valgus deformity and medial stretching is the characteristic picture.

A correctable valgus deformity means limited lateral bone loss and an uncontracted lateral side. 4.3.10 covers the deformity.

Medial laxity with a valgus deformity means the medial side has lengthened and the deformity is structural. 4.12.5 covers the posterior oblique ligament.

A history of lateral meniscectomy or a lateral tibial plateau fracture explains the pattern and makes it post traumatic rather than primary. 4.9.10 covers meniscal deficiency.

Symmetrical valgus knees with inflammatory features point away from mechanical wear. 4.8.9 covers synovitis.

MRCS Level

How It Is Performed

In a viva this is the valgus knee station and the expected answer names the secondary causes early.

The expected points are the standing alignment, the gait, the lateral joint line, the correctability, the medial ligament, the range, the rotational component and the history of trauma or inflammation.

Say that you would ask about previous lateral meniscal surgery and plateau fracture, since both produce this pattern. 4.9.10 covers meniscal deficiency.

Say that you would look for inflammatory features and examine other joints, because symmetrical valgus knees suggest a systemic cause. 4.8.9 covers synovitis.

Say that you would assess the hip, since a valgus knee alters hip loading and referred pain is common in this age group. 4.2.15 covers referred pain.

What a Positive Means

The reasoning expected is that lateral wear lowers the lateral side, the limb angulates into valgus, the lateral load rises, and the cycle continues in the mirror image of the varus pattern. 3.5.2 covers contact pressures.

The medial side lengthens under the sustained valgus, which is why medial laxity accompanies an established deformity. 4.12.5 covers the posterior oblique ligament.

Valgus wear commonly carries an external rotation and a flexion component, which is why the deformity is not purely coronal. 4.19.7 covers torsional assessment.

A lateral meniscectomy removes the lateral load distribution, so the lateral compartment wears faster, which is why the history matters. 4.9.10 covers meniscal deficiency.

How Good It Is

The examination is reliable for the direction and the presence of the deformity and for the medial laxity.

Its best contribution is the history of a secondary cause, which changes the whole assessment and which no imaging asks about. 4.2.9 covers the onset.

It is imprecise about the magnitude and poor at separating the femoral and the tibial contributions.

Long leg films measure the deformity and localise it, so the examination contributes the soft tissue state and the cause. 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 a valgus knee is sorted by magnitude, correctability, the state of the medial side and whether the cause is primary or secondary.

A moderate correctable valgus deformity with lateral pain and a competent medial side is the group where load redistribution is considered, and the examination identifies it. 4.20.4 covers the osteotomy assessment.

A fixed valgus deformity with medial laxity sits outside it, because correcting the alignment alone leaves the medial side long. 4.12.5 covers the posterior oblique ligament.

An inflammatory cause changes the treatment entirely, so the examination for other joints and for systemic features is part of the decision. 4.8.9 covers synovitis.

Lateral wear in a young patient after meniscectomy is a different problem from primary wear in an older one, and the examination finds the difference by history. 4.9.10 covers meniscal deficiency.

Where It Misleads

The commonest error is recording the deformity supine, where valgus understates itself as much as varus does. 4.3.3 covers standing alignment.

Medial laxity in a valgus knee can be relative rather than absolute, since the shortened lateral side makes a normal medial side look long. 4.12.5 covers it.

A valgus knee with an external rotation component is described as a pure coronal deformity, which loses information the correction needs. 4.19.7 covers torsional assessment.

Inflammatory disease is attributed to mechanical wear when the knees are examined one at a time rather than compared. 4.1.4 covers the structured approach.

Medial laxity measured in extension in a knee with a flexion deficit is unreliable, since the position changes the restraint being tested. 4.12.3 covers the assessment in flexion.

Fellowship Level

Where It Misleads

At fellowship level the valgus knee is harder than the varus knee, because its deformity is more often multiplanar and its secondary causes are more varied.

The combination of valgus, external rotation and fixed flexion is common, and the examination describes the first two poorly and the third well. 4.5.4 covers the flexion deformity.

Medial lengthening and lateral bone loss produce the same clinical laxity, and the examination cannot separate them in a single assessment. 4.12.5 covers the posterior oblique ligament.

A valgus knee after a plateau fracture carries a joint line that is not where the examination assumes, which affects every localising sign. 4.6.4 covers the technique.

Peroneal nerve function is examined in a valgus knee as a preoperative baseline, not as a diagnostic step, and omitting it creates a later problem. 4.6.10 covers the popliteal fossa.

The examination cannot say whether the lateral compartment has bone loss or cartilage loss alone, and the distinction changes the correction. 4.17.5 covers articular defects.