Patellofemoral Arthritis, Examination

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Patellofemoral Arthritis

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For Medical Students

What It Tests

Patellofemoral arthritis is loss of the articular surface between the patella and the trochlea, and it produces pain on loaded flexion with crepitus and tenderness.

The examination distinguishes it from patellofemoral pain without structural change by the crepitus, the age, the pattern and the response to compression. 4.15.9 covers the alternative.

It also distinguishes it from tibiofemoral arthritis, which matters because the compartments are treated differently. 4.18.5 covers the arthritic assessment.

How It Is Performed

Take the history: pain on stairs and on rising from a chair, worse going down than up, with stiffness after sitting. 4.2.11 covers aggravating factors.

Assess the patellar facets by displacement and palpation, noting diffuse rather than focal tenderness. 4.6.5 covers patellar tenderness.

Assess the painful arc, with and without patellar compression, and note crepitus felt under the hand as the knee moves. 4.7.6 covers the arc.

Assess the tibiofemoral compartments, the joint lines and the alignment, since isolated patellofemoral arthritis is less common than the combined pattern. 4.5.1 covers the mechanical axis.

Assess the range and the quadriceps, which are what limit the patient functionally. 4.7.9 covers functional range.

What a Positive Means

Diffuse facet tenderness with crepitus and a painful mid to deep flexion arc indicates patellofemoral articular change.

Pain worse descending stairs than ascending is characteristic, because descent loads the joint eccentrically through a larger arc. 3.12.3 covers contact pressures.

Crepitus without pain is a common finding in people with no complaint and is not a diagnosis.

Tibiofemoral joint line tenderness alongside indicates the combined pattern, which is commoner than the isolated one and is treated as a whole joint problem. 4.18.2 covers established arthritis.

A history of a previous dislocation or of maltracking suggests the arthritis is secondary to the mechanics, which changes the conversation about what caused it. 4.15.1 covers tracking.

Key Learning Points

Diffuse facet tenderness with crepitus and a painful flexion arc indicates articular change.
Pain worse descending than ascending stairs is characteristic.
Crepitus without pain is common and is not a diagnosis.
Tibiofemoral tenderness alongside indicates the combined pattern, which is commoner.
A history of dislocation or maltracking suggests secondary arthritis.

MRCS Level

How It Is Performed

In a viva the distinction from the non structural diagnosis and from tibiofemoral arthritis are the two things worth getting right.

The expected points are the history pattern, the diffuse facet tenderness, the arc with compression, the crepitus, the tibiofemoral assessment and the alignment.

Say that descent hurts more than ascent and say why, because the mechanism is the question behind it. 3.12.3 covers contact pressures.

Say that you would assess the tibiofemoral compartments, since isolated patellofemoral arthritis is the minority. 4.18.5 covers that pattern.

Say that radiographs including a skyline view are what grade it, and that the examination localises. 4.1.6 covers that relationship.

What a Positive Means

The reasoning expected is that patellofemoral contact pressure is high and rises with flexion, so a damaged surface is loaded most in the arc where the patient hurts. 3.12.2 covers contact areas.

Descending stairs loads the extensor mechanism eccentrically over a large arc, which is why that task discriminates better than ascent. 3.3.12 covers kinematics during stair climbing.

Maltracking concentrates load on one facet, which is the mechanism behind secondary patellofemoral arthritis and the reason the history of instability matters. 3.12.10 covers patellofemoral arthritis.

The joint's isolation is unusual because the same mechanical and biological factors affect the tibiofemoral compartments, which is why the whole joint is assessed. 3.5.3 covers load distribution.

How Good It Is

The examination localises the arthritis to the patellofemoral joint reasonably well and cannot grade it, which is the familiar division.

Crepitus is the most specific finding and is also present in asymptomatic knees, so it needs a matching complaint.

The pattern of pain is more useful than any physical finding, which makes the history the stronger instrument here. 4.2.11 covers aggravating factors.

Radiographs grade it, and a skyline view is required, which is a practical point worth knowing because it is frequently omitted. 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

Patellofemoral contact pressure is high and rises with flexion, so a damaged surface hurts in that arc.
Descent loads the extensor mechanism eccentrically over a large arc.
Maltracking concentrates load on one facet, which is how secondary arthritis arises.
Isolation is unusual, because the same factors affect the other compartments.
A skyline view is required and is frequently omitted.

FRCS Level

How Good It Is

At decision level the examination separates isolated patellofemoral arthritis from the combined pattern, and that separation decides the operation.

Isolated patellofemoral arthritis in a younger patient with maltracking is a group in which a mechanical correction has a case, and the examination raises the mechanical factor. 4.15.1 covers tracking.

Isolated arthritis in an older patient with a central track is a group in which a patellofemoral replacement is discussed, and the examination's contribution is establishing the isolation. 4.20.7 covers partial replacement.

The combined pattern is a whole joint problem, and the examination's finding of tibiofemoral tenderness is what moves it there. 4.18.2 covers established arthritis.

In every group the quadriceps and the range set what any operation can achieve, and they are what the examination follows. 4.7.9 covers functional range.

Where It Misleads

The commonest error is diagnosing it from crepitus alone.

The second is not assessing the tibiofemoral compartments, which overstates the isolation.

The third is not obtaining a skyline view.

The fourth is reading the pain pattern as non structural in a patient whose examination shows crepitus and whose age fits. 4.15.9 covers that alternative.

The fifth is offering a patellofemoral procedure in a knee whose tibiofemoral compartments are also affected.

Key Learning Points

The separation of isolated from combined arthritis decides the operation.
A younger patient with maltracking is a group where a mechanical correction has a case.
An older patient with a central track is where a patellofemoral replacement is discussed.
Tibiofemoral tenderness moves the problem to a whole joint one.
The quadriceps and the range set what any operation can achieve.

Fellowship Level

Where It Misleads

In referred practice patellofemoral arthritis is most often relevant as the later consequence of something that was treated earlier.

A patient with recurrent dislocations treated decades ago and patellofemoral arthritis now has secondary change, and that trajectory belongs in the conversation with the patients being treated today. 3.12.10 covers it.

A patient with a tubercle osteotomy and progressive patellofemoral arthritis may have had a correction that unloaded one facet and loaded another, and the pre-operative imaging is needed to interpret it. 4.6.7 covers the tubercle.

A patient with patellofemoral arthritis after a patellofemoral replacement has either progression into the other compartments or a malpositioned implant, and the examination separates those by where the tenderness is. 4.20.7 covers partial replacement.

A patient with isolated patellofemoral arthritis and a valgus limb has an alignment contribution, and operating on the joint without the limb repeats the mechanism. 4.5.3 covers valgus alignment.

In medicolegal work attributing patellofemoral arthritis to a single injury is usually unsupportable unless a dislocation or an osteochondral injury is documented. 4.23.7 covers that setting.

Key Learning Points

It is most often the later consequence of something treated earlier.
Recurrent dislocations treated decades ago produce secondary change, which belongs in today's conversation.
A correction can unload one facet and load another.
Arthritis after a patellofemoral replacement is progression or malposition, separated by the tenderness.
Attribution to a single injury is usually unsupportable without a documented dislocation or osteochondral injury.

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.

Safety. KneeSchool is educational and does not give individual medical advice. Seek urgent assessment for a knee that cannot bear weight after an injury, a hot swollen knee with a fever, or new numbness, weakness or coldness in the leg or foot.