MPFL Reconstruction, Examination of the Knee

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MPFL Reconstruction

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What It Tests

After a medial patellofemoral ligament reconstruction the examination is checking the patellar translation, the tracking, the range and whether the apprehension has gone. 4.15.7 covers the medial restraint assessment.

The examination is looking for two opposite failures, which are residual instability and a patella held too tightly. 4.15.4 covers patellar glide.

It matters that the underlying anatomy is usually unchanged, so the trochlear shape and the alignment still matter. 4.15.8 covers trochlear dysplasia.

How It Is Performed

Establish what was done, with what graft, whether anything else was corrected and when. 4.2.30 covers previous surgery.

Look at the scars, which indicate the graft and any concurrent procedure. 4.3.7 covers surgical scars.

Assess the effusion and the range, since stiffness after this operation is a recognised problem. 4.7.10 covers the post operative range assessment.

Assess the patellar translation laterally, comparing it with the other side and with the preoperative record. 4.15.4 covers patellar glide.

Assess the medial translation, because a patella that will not move medially has been tethered. 4.15.4 covers patellar glide.

Assess the patellar tilt, since an over tightened reconstruction tilts the patella medially. 4.15.5 covers patellar tilt.

Assess apprehension, which should have resolved. 4.15.3 covers the apprehension test.

Watch the tracking through the range for a residual lateral deviation. 4.15.1 covers patellar tracking.

What a Positive Means

Reduced lateral translation, no apprehension, a full range and normal tracking is the expected result.

Persistent lateral translation with apprehension indicates the reconstruction has not restrained the patella, or the underlying anatomy dominates. 4.15.8 covers trochlear dysplasia.

Reduced medial translation with medial tilt indicates an over tightened reconstruction, which produces medial pain and a stiff patella. 4.15.5 covers patellar tilt.

A restricted flexion range after this operation suggests the graft is tight in flexion. 4.7.4 covers the flexion assessment.

Anterior pain with a stable patella raises the medial facet loading that over tightening produces. 4.6.5 covers patellar tenderness.

Key Learning Points

The examination looks for residual instability and for over tightening.
Medial translation is assessed as well as lateral translation.
A medially tilted patella suggests over tightening.
Restricted flexion suggests the graft is tight in flexion.
The underlying trochlear shape is usually unchanged.

MRCS Level

How It Is Performed

In a viva this is the post patellar stabilisation station and the expected answer tests both directions of translation.

The expected points are the operation and the graft, the scars, the effusion, the range, the lateral and the medial translation, the tilt, the apprehension and the tracking.

Say that you would assess medial translation, and give the reason. 4.15.4 covers patellar glide.

Say that you would assess the trochlear shape and the alignment, since the reconstruction does not change either unless they were addressed. 4.15.8 covers trochlear dysplasia.

Say that you would record the preoperative findings for comparison. 4.1.8 covers examination documentation.

What a Positive Means

The reasoning expected is that the medial restraint resists lateral translation near extension, where the trochlea does not yet contain the patella. 3.12.5 covers the function of the medial restraint.

A reconstruction that is too tight raises the medial facet load, which is why over tightening produces pain rather than instability. 3.12.3 covers contact pressures.

A reconstruction cannot compensate for a severely dysplastic trochlea, which is why the shape governs the expected result. 3.12.4 covers trochlear function.

A graft fixed at the wrong length behaves differently through the range, which is why flexion is tested as well as translation. 3.12.1 covers patellar tracking.

How Good It Is

The examination establishes the restraint and the tethering reliably, because both are direct findings.

Its best contribution is the pair of translation tests, which catch both failure modes in one assessment. 4.15.4 covers patellar glide.

It cannot assess graft position or fixation.

Cross sectional imaging assesses the anatomy and the graft, so the examination establishes the function. 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.

Key Learning Points

The medial restraint works near extension, before the trochlea contains the patella.
An over tightened graft raises the medial facet load and produces pain.
A reconstruction cannot compensate for a severely dysplastic trochlea.
A graft fixed at the wrong length behaves differently through the range.
The pair of translation tests catches both failure modes.

FRCS Level

How Good It Is

At decision level the examination separates residual instability, over tightening, stiffness and an unaddressed anatomical cause.

Residual instability with a dysplastic trochlea or a torsional abnormality is a different problem from a failed graft, and the examination raises the distinction. 4.19.7 covers torsional assessment.

Medial pain with reduced medial translation is over tightening, and the examination is the only way that is identified. 4.15.5 covers patellar tilt.

Stiffness with a stable patella is a rehabilitation or a graft tension problem, and the range through flexion separates them. 4.7.4 covers the flexion assessment.

Anterior pain with a stable patella after this operation raises patellofemoral cartilage damage from the original dislocations. 4.17.5 covers articular cartilage defects.

Where It Misleads

The commonest error is assessing lateral translation only, so over tightening is missed. 4.15.4 covers patellar glide.

Translation is compared against the other knee, which is usually abnormal too in this group. 4.1.4 covers the structured approach.

Apprehension reported after the operation is attributed to instability when it can be anxiety. 4.15.3 covers the apprehension test.

Anterior pain is attributed to the graft when the cartilage was damaged at the first dislocation. 4.2.22 covers the dislocation event.

An unaddressed torsional or trochlear abnormality is attributed to graft failure. 4.15.8 covers trochlear dysplasia.

Key Learning Points

Assessing lateral translation only misses over tightening.
The opposite knee is usually abnormal too in this group.
Apprehension after the operation can be anxiety rather than instability.
Cartilage damage from the first dislocation causes later anterior pain.
Unaddressed anatomy is attributed to graft failure.

Fellowship Level

Where It Misleads

At fellowship level the examination has to decide whether a symptomatic stabilisation failed, was over tightened, or was the wrong operation.

The three present differently and overlap, since a tight graft in a dysplastic knee can give both pain and residual instability. 4.15.8 covers trochlear dysplasia.

Graft tension is assessed through translation at one or two angles, and the graft's behaviour through the whole range is what matters. 4.15.1 covers patellar tracking.

Patellar cartilage damage accumulates with each dislocation, so the pain after a successful stabilisation is often not about the stabilisation. 4.17.5 covers articular cartilage defects.

Torsional and coronal contributions are not corrected by this operation, and their persistence is read as graft failure. 4.19.7 covers torsional assessment.

The examination cannot assess the graft's fixation or its tunnel position, which determine the result more than the tension assessed clinically. 4.15.7 covers the medial restraint assessment.

Key Learning Points

Failure, over tightening and the wrong operation overlap in presentation.
Translation at one or two angles does not describe the whole range.
Cartilage damage from previous dislocations explains much of the later pain.
Uncorrected torsional and coronal contributions are read as graft failure.
Fixation and tunnel position matter more than clinically assessed tension.

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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