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Valgus Stress Testing

Page 4.12.1 · Medial Knee Examination · examination page

One manoeuvre performed at two angles, and the reason reading it as one test throws away most of what it tells you.

Pipeline status. Editorial draft. Evidence verification did not run. Not consultant reviewed. Not for clinical use.

The same topic at 4 depths

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Valgus Stress Testing

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For Medical Students

What It Tests

Valgus stress testing measures how far the medial side of the knee opens when the joint is pushed into valgus, and it tests the medial restraints.

The medial side is not one structure. The superficial medial collateral ligament, the deep medial ligament and the posterior oblique ligament all resist valgus, and they do it in different amounts at different flexion angles. 3.9.1 covers valgus stability.

That is why the test is performed twice. At thirty degrees the superficial ligament dominates, and in full extension the cruciates and the posteromedial structures carry a share. 3.9.9 covers the contributions at different angles.

How It Is Performed

Lay the patient supine with the leg relaxed and the knee straight.

Hold the ankle in one hand and place the other hand along the lateral side of the knee, with your fingers over the medial joint line so you can feel it open.

Apply a valgus force through the ankle while the hand at the knee acts as the fulcrum, and feel the medial joint line with your fingers rather than watching the foot.

Record the amount of opening and the quality of the endpoint, then repeat the whole thing with the knee flexed to thirty degrees.

Compare both angles with the other knee before drawing any conclusion. 4.1.2 covers the principle.

What a Positive Means

Increased opening with a soft endpoint indicates that the medial restraints are deficient at the angle tested.

Opening at thirty degrees with a firm endpoint in extension points at the superficial ligament in isolation, which is the commonest medial injury and the one that usually heals. 4.12.3 covers that angle.

Opening in full extension as well means more than the superficial ligament is torn, and in practice that means a cruciate or the posteromedial corner. 4.12.2 covers extension.

The endpoint matters as much as the amount. An increase with a firm endpoint suggests a stretched but continuous ligament; a soft or absent endpoint suggests a complete disruption.

Key Learning Points

  • One manoeuvre, two angles, and the two angles mean different things.
  • At thirty degrees the superficial medial ligament dominates the restraint.
  • Opening in full extension implicates a cruciate or the posteromedial corner.
  • Feel the medial joint line with your fingers rather than watching the foot.
  • A firm endpoint with increased opening suggests a stretched but continuous ligament.

MRCS Level

How It Is Performed

In a viva the mark is in saying both angles without being prompted, and in saying why each one is tested.

The expected points are the relaxed leg, the hand as a fulcrum, the fingers on the joint line, the endpoint, both angles, and the comparison.

Say that you would stabilise the hip, because an unstabilised limb rotates externally and an externally rotated leg opens medially for reasons that have nothing to do with the ligament.

Say that you would grade the opening against the other side rather than in millimetres at the bedside, and that stress radiographs are what convert it into a number. 4.12.3 covers grading.

Say that you would examine the cruciates in the same sitting, because a medial injury with a cruciate injury is a different problem from either alone. 3.9.10 covers that combination.

What a Positive Means

The reasoning expected is that each medial structure has a flexion range in which it contributes most, so the pattern across the two angles localises the injury where a single reading cannot. 3.9.9 covers the angles.

The superficial ligament is the principal valgus restraint through mid flexion, and it is the structure a thirty degree test is reading. 3.9.3 covers its function.

The deep ligament attaches to the meniscus and contributes less to valgus restraint than to rotational control, which is why it is not isolated by this test at all. 4.12.4 covers it.

The posterior oblique ligament tightens in extension and is what makes a knee with a torn superficial ligament still feel firm in full extension. 3.9.5 covers its function.

How Good It Is

Valgus stress testing is the most reliable collateral examination in the knee and more reproducible than any rotational test, because the direction of force is simple and the joint line is palpable.

It grades the superficial ligament well and localises within the medial side poorly, which is the division of labour this chapter keeps returning to.

It performs well in the acute knee, better than most of the cruciate tests, because valgus does not require the patient to tolerate deep flexion.

Its weakness is the uninjured comparison. Physiological medial laxity is common and symmetrical, so an uncompared grade is close to useless. 4.23.3 covers hypermobile patients.

No figures appear for any of these comparisons, under decision 023, and the comparison is the claim being made.

Key Learning Points

  • The pattern across two angles localises the injury where a single reading cannot.
  • The deep ligament contributes more to rotational control than to valgus restraint.
  • The posterior oblique ligament is why a torn superficial ligament can feel firm in extension.
  • The test grades the superficial ligament well and localises within the medial side poorly.
  • Physiological medial laxity is common and symmetrical, so the comparison carries the test.

FRCS Level

How Good It Is

At decision level the grade decides the treatment of the medial side, and it is one of the few examination findings in this section that does so directly.

A first or second degree injury with a firm endpoint in extension is treated non operatively in almost every case, because the superficial ligament heals in continuity and heals well.

A third degree injury with opening in extension is where the decision becomes real, and what settles it is usually the posteromedial corner rather than the grade. 4.12.5 covers that assessment.

A medial injury alongside an anterior cruciate rupture changes the sequence rather than the decision. The medial side is given time, and the examination repeated at six weeks is what decides whether the cruciate reconstruction proceeds alone. 3.9.10 covers the combination.

Stress radiographs are worth obtaining where the plan turns on the difference between second and third degree, since that is where the clinical grade is least reproducible.

Where It Misleads

The commonest error is testing one angle, which collapses two findings into one and loses the information the second angle carries.

The second is an unstabilised limb, where external rotation of the whole leg reads as medial opening.

The third is reading a grade without an endpoint, which is the same error the cruciate chapters describe and has the same consequence at the next visit. 4.1.8 covers the record.

The fourth is examining a swollen knee and recording a firm endpoint that is hamstring spasm rather than ligament.

Key Learning Points

  • The grade decides the treatment of the medial side directly, which is unusual in this section.
  • A third degree injury's decision usually turns on the posteromedial corner rather than the grade.
  • A medial injury with a cruciate rupture changes the sequence rather than the decision.
  • Stress radiographs earn their place where second and third degree have to be separated.
  • Testing one angle collapses two findings into one.

Fellowship Level

Where It Misleads

In referred practice the question is rarely whether the medial side is lax. It is whether the laxity that remains matters, and the examination answers that better than any image.

A patient with residual medial laxity, a firm endpoint and no symptoms after a healed injury is common and needs nothing. 4.12.8 covers that assessment.

A patient with persistent valgus laxity and an anteromedial rotatory pattern has a posteromedial corner that did not heal, and that is a different diagnosis reached by adding rotation to the test. 4.12.6 covers it.

Valgus laxity after an anterior cruciate reconstruction is the finding most often dismissed and most often responsible for the graft that stretched, since an uncontrolled medial side loads the graft in the plane it least resists. 4.10.11 covers post-reconstruction assessment.

A knee that opens medially with a varus alignment is a mechanical problem as well as a ligament one, and an isolated medial reconstruction into that limb is a recognised route to recurrence.

In a knee with previous medial surgery the endpoint may be firm over a joint that still opens, because scar substitutes for ligament and the two feel different only with experience. 4.2.30 covers previous surgery.

Key Learning Points

  • The question in referred practice is whether the remaining laxity matters, not whether it exists.
  • Persistent laxity with a rotatory pattern means the posteromedial corner did not heal.
  • Medial laxity after a cruciate reconstruction is often dismissed and often why the graft stretched.
  • Medial opening with varus alignment is a mechanical problem as well as a ligament one.
  • Scar after previous medial surgery gives a firm endpoint over a joint that still opens.

Explore Further

Where this topic came from and where it goes next in the spiral.

References

No reference list is attached to this draft. Evidence verification has not run, because source retrieval was unavailable at generation time. Under the Operations Handbook a missing reference is acceptable and an invented one is a critical failure, so nothing has been cited and no citation marker appears in the text. This page carries no diagnostic accuracy figure, which is decision 023 rather than an omission. The comparative standing of these tests is standard teaching and a specific sensitivity written from memory is the same class of claim as an invented citation, so ACC-001 refuses the number and the page states the comparison. A reviewer with the literature can add the figures into How Good It Is without restructuring the page, and chapter 3.17 lists the studies the figures would come from. Any measurement here, including a flexion angle, is written from standard teaching, has not been checked, and is registered under decision 006 in pipeline/config/figures with a verification state of UNVERIFIED_FROM_MEMORY.

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