Patellar Glide

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Student MRCS FRCS Fellow

For Medical Students

What It Tests

Patellar glide measures how far the patella can be displaced medially and laterally with the knee extended and the quadriceps relaxed.

It measures the restraints rather than the symptom, which is the complement of the apprehension test. 4.15.3 covers that test.

The conventional grading is in quadrants of the patella's width: displacement by one, two, three or four quadrants, with the fourth meaning the patella can be dislocated. 2.4.1 covers the patellar anatomy.

How It Is Performed

Lay the patient supine with the knee extended and fully relaxed, and support the limb so the patient does not hold it.

Grasp the patella between finger and thumb and displace it laterally, noting how many quadrants of its width it moves.

Displace it medially and note the same.

Repeat with the knee flexed to about thirty degrees, since the patella engages the trochlea there and the glide should reduce.

Compare both knees, because the normal range of glide varies widely and only the comparison is interpretable. 4.23.3 covers hypermobile patients.

What a Positive Means

Increased lateral glide indicates a deficient medial restraint, principally the medial patellofemoral ligament. 2.12.2 covers it.

Lateral displacement of three quadrants or more, or the ability to displace the patella over the lateral edge, indicates substantial medial deficiency.

Reduced medial glide indicates a tight lateral structure, which is a different problem and is associated with pain rather than instability. 4.15.5 covers the tilt that accompanies it.

A glide that does not reduce when the knee is flexed to thirty degrees suggests the patella is not engaging the trochlea, which raises dysplasia or patella alta. 4.15.8 covers dysplasia.

Symmetrically increased glide in both knees is generalised hypermobility and is not a diagnosis on its own. 4.23.3 covers those patients.

Key Learning Points

Glide measures the restraints, where the apprehension test reads the symptom.
The grading is in quadrants of the patella's width.
Increased lateral glide indicates a deficient medial restraint.
Reduced medial glide indicates a tight lateral structure and is associated with pain.
Symmetrically increased glide in both knees is hypermobility, not a diagnosis.

MRCS Level

How It Is Performed

In a viva the quadrant grading is the expected vocabulary, and testing at two flexion angles is what demonstrates understanding.

The expected points are the relaxed extended knee, the lateral and medial glide in quadrants, the repeat at thirty degrees, and the comparison.

Say that you would test at thirty degrees as well, and say why: the patella should engage the trochlea and the glide should fall. 4.15.8 covers the structure that makes that happen.

Say that a relaxed quadriceps is essential, since a contracted quadriceps holds the patella and makes every glide read as reduced.

Say that you would record both directions and both angles, because a tight lateral side and a lax medial side are different findings that can coexist. 4.1.8 covers the record.

What a Positive Means

The reasoning expected is that the medial patellofemoral ligament provides most of the restraint to lateral displacement in the first part of flexion, so its loss increases the lateral glide specifically near extension. 3.12.5 covers its function.

The trochlea takes over as the knee flexes, which is why the glide falls at thirty degrees in a normal knee and does not in a dysplastic one. 3.12.4 covers trochlear function.

The lateral retinaculum resists medial displacement, so a tight lateral structure reduces the medial glide and tilts the patella. 2.12.4 covers the retinacula.

A patella that can be displaced over the lateral edge has lost both the soft tissue restraint and the bony constraint, which is why that finding is the most significant. 3.12.8 covers patellar instability.

How Good It Is

Glide is more reproducible than most patellofemoral findings, because the quadrant grading gives a scale, and it remains dependent on relaxation.

It measures the restraint well and predicts the complaint poorly, since many people with increased glide have no instability. 4.15.3 covers the test that predicts it better.

It is most useful in combination: an increased lateral glide with apprehension is a stronger finding than either alone.

It cannot distinguish a deficient ligament from generalised laxity, which the systemic assessment does in seconds. 4.23.3 covers those patients.

No figures appear for any accuracy comparison on this page, under decision 023, and the comparison is the claim being made.

Key Learning Points

The medial patellofemoral ligament provides most of the restraint in early flexion.
The trochlea takes over as the knee flexes, which is why the glide falls at thirty degrees.
The lateral retinaculum resists medial displacement, so tightness reduces medial glide.
Displacement over the lateral edge means both soft tissue and bony constraint are lost.
It measures the restraint well and predicts the complaint poorly.

FRCS Level

How Good It Is

At decision level the glide contributes to what is reconstructed and to whether a lateral structure needs addressing.

An increased lateral glide with instability contributes to the case for a medial patellofemoral ligament reconstruction, alongside the bony assessment. 4.15.7 covers the ligament.

A reduced medial glide with a tilted patella and anterior pain is a lateral tightness problem, and it is treated differently and more conservatively than instability. 4.15.5 covers the tilt.

A glide that does not reduce at thirty degrees raises dysplasia or patella alta and moves the decision towards a bony procedure. 4.15.8 covers it.

Symmetrical hypermobility changes the expected outcome of a reconstruction rather than the decision to perform one, and that belongs in the consent. 4.23.3 covers those patients.

Where It Misleads

The commonest error is testing with the quadriceps contracted.

The second is testing in one direction only, which misses a tight lateral side.

The third is testing at one angle, which misses the engagement question.

The fourth is reading increased glide as instability in a patient with no apprehension and no episodes. 4.15.3 covers that distinction.

The fifth is comparing with a population normal rather than with the other knee.

Key Learning Points

Increased lateral glide with instability supports a ligament reconstruction.
Reduced medial glide with a tilted patella is a lateral tightness problem.
A glide that does not reduce at thirty degrees moves the decision towards a bony procedure.
Hypermobility changes the expected outcome rather than the decision.
Testing with the quadriceps contracted makes every glide read as reduced.

Fellowship Level

Where It Misleads

In referred practice the glide is most useful after surgery, where it says whether the reconstruction is doing its job and whether it is doing too much.

A patient with a reconstructed ligament and an increased lateral glide has a failed or stretched graft, and that is a clearer finding than any imaging. 4.20.6 covers that assessment.

A patient with a reduced glide in both directions after a reconstruction is over constrained, and the presentation is medial facet pain and stiffness rather than instability. 4.6.5 covers patellar tenderness.

A patient with an increased glide, no instability and no complaint needs nothing, and operating on the measurement is the error this page guards against. 4.15.3 covers the finding that would change that.

In a knee with a previous lateral release the medial glide is increased for a surgical reason, and a medial instability after a release is a recognised complication. 4.2.30 covers previous surgery.

In a hypermobile patient a graft tensioned to the contralateral glide reproduces the laxity, so tensioning to a target instead is a deliberate decision. 4.23.3 covers those patients.

Key Learning Points

After a reconstruction an increased lateral glide is a clearer finding than any imaging.
A reduced glide in both directions is over constraint, presenting as pain and stiffness.
An increased glide with no instability and no complaint needs nothing.
After a lateral release the medial glide is increased for a surgical reason.
In a hypermobile patient the tensioning target is a deliberate decision.

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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