Articular Cartilage Defects

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Articular Cartilage Defects

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Student MRCS FRCS Fellow

For Medical Students

What It Tests

An articular cartilage defect is a loss of the surface without the bone beneath it being avulsed, so there is nothing to fix back and the question becomes whether to resurface. 4.17.3 covers the version with bone attached.

The examination's job is to establish whether the defect is symptomatic, which is a different question from whether it exists. 4.17.1 covers the presentation.

That distinction is the content of this page. Defects are found incidentally often enough that treating the image rather than the patient is a recognised error. 4.17.6 covers the assessment that prevents it.

How It Is Performed

Establish which compartment the pain is in, and whether it matches the defect's compartment on the imaging. 4.6.4 covers joint line tenderness.

Assess the painful arc, since a defect is loaded at a particular flexion angle and the arc should match its position. 4.7.6 covers the arc.

Assess the effusion, since a recurrent activity related effusion is the most useful sign that a defect is symptomatic. 4.8.3 covers the bulge sign.

Ask about mechanical symptoms, since a delaminated flap catches and that changes the decision. 4.17.2 covers them.

Assess the alignment, since it determines whether the compartment carrying the defect is being loaded. 4.5.1 covers the mechanical axis.

Assess the meniscal status in that compartment, since a deficient meniscus concentrates the load on the surface. 4.9.10 covers meniscal deficiency.

What a Positive Means

Compartment pain matching the defect's compartment, a matching painful arc and a recurrent effusion together indicate a symptomatic defect.

A defect on imaging with pain in a different compartment, or with diffuse pain, is a finding rather than a diagnosis. 4.17.1 covers that argument.

A mechanical symptom with a defect raises a delaminated flap, which is a different and more immediately treatable problem. 4.17.2 covers it.

A malaligned limb loading the defect's compartment makes the alignment part of the problem and part of the treatment. 4.5.2 covers varus alignment.

A deficient meniscus in the same compartment concentrates the load and is part of the same mechanical story. 4.9.10 covers it.

Key Learning Points

There is no bone to fix back, so the question is whether to resurface.
The examination establishes whether the defect is symptomatic, not whether it exists.
Compartment pain, a matching arc and a recurrent effusion together indicate a symptomatic defect.
A defect with pain elsewhere or diffuse pain is a finding rather than a diagnosis.
Alignment and meniscal status are part of the same mechanical story.

MRCS Level

How It Is Performed

In a viva the distinction between a defect and a symptomatic defect is the answer, and the matching of the compartment and the arc is how it is made.

The expected points are the compartment, the arc, the effusion, the mechanical history, the alignment and the meniscal status.

Say that an incidental defect is common and that treating it is an error, which is the clinically important negative. 4.17.1 covers it.

Say that the alignment and the meniscus are assessed because a resurfacing procedure fails in a compartment that is overloaded. 4.5.1 covers the measurement.

Say that the functional assessment establishes whether the defect limits the patient, which is the question treatment answers. 4.17.6 covers it.

What a Positive Means

The reasoning expected is that a defect concentrates load on its rim and on the exposed subchondral bone, so pain comes from the bone and from the altered contact rather than from the cartilage. 3.5.2 covers contact pressures.

Load concentration depends on the compartment's share of the limb's load, which is why alignment determines whether a defect is symptomatic. 3.5.6 covers the effects of malalignment.

The meniscus distributes load across the compartment, so its loss raises the peak pressure on a defect and is part of the same problem. 3.5.5 covers the effects of meniscal loss.

The flexion angle at which a defect is loaded depends on its position, which is why the arc should match the imaging and why a mismatch matters. 3.5.4 covers the effects of flexion.

How Good It Is

The examination cannot detect a defect and can establish whether a known defect is likely to be the source, which is the useful question.

Its most specific contribution is the match between the painful arc and the defect's position, which is an underused check. 4.7.6 covers it.

The recurrent activity related effusion is the most useful single sign and is shared with other diagnoses. 4.8.8 covers chronic effusions.

Imaging grades the defect and says nothing about whether it matters, which is the division this page rests on. 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

Load concentrates on a defect's rim and on exposed subchondral bone, which is the pain source.
Alignment determines the compartment's share of load and therefore whether a defect is symptomatic.
Meniscal loss raises the peak pressure on a defect.
The arc should match the defect's position, and a mismatch matters.
Imaging grades the defect and says nothing about whether it matters.

FRCS Level

How Good It Is

At decision level the examination decides whether a defect is treated at all, and the alignment and meniscal findings decide whether a treatment can survive.

A symptomatic defect in a malaligned limb is an alignment problem first, and resurfacing without correction loads the repair. 4.5.2 covers varus alignment.

A symptomatic defect with a deficient meniscus in the same compartment is a meniscal problem as well, and both have to be addressed for either to work. 4.9.10 covers meniscal deficiency.

An incidental defect in a patient whose symptoms do not match it is not treated, and the examination is what establishes the mismatch. 4.17.1 covers it.

A delaminated flap with mechanical symptoms is treated more readily, because the mechanical problem has a reliable answer where the pain does not. 4.17.2 covers them.

Where It Misleads

The commonest error is treating the image rather than the patient.

The second is not checking the arc against the defect's position.

The third is resurfacing in a malaligned limb.

The fourth is resurfacing in a compartment with a deficient meniscus without addressing that.

The fifth is attributing a recurrent effusion to the defect without excluding a synovial cause. 4.8.9 covers synovitis.

Key Learning Points

The examination decides whether a defect is treated; alignment and meniscal status decide survival.
Resurfacing without correcting a malaligned limb loads the repair.
A deficient meniscus in the same compartment has to be addressed for either to work.
A delaminated flap is treated more readily, because the mechanical problem has a reliable answer.
Treating the image rather than the patient is the commonest error.

Fellowship Level

Where It Misleads

In referred practice the cartilage defect is the finding an operation was offered for, and the referral is usually about why it did not work.

A patient with a resurfaced compartment, a persisting complaint and an uncorrected alignment had the surface treated and the mechanics left. 4.5.1 covers the measurement.

A patient with a resurfaced compartment and a deficient meniscus has the same problem through a different route. 4.9.10 covers meniscal deficiency.

A patient whose symptoms never matched the defect's compartment had an incidental finding treated, and the original examination is where that should have been caught. 4.17.1 covers it.

A patient with a large defect, a well aligned limb and an intact meniscus who is functionally limited is the group in which resurfacing has its best case, and the functional assessment is what identifies them. 4.17.6 covers it.

In medicolegal work attributing a cartilage defect to a single injury needs an acute mechanism and early imaging, and most defects have neither. 4.23.7 covers that setting.

Key Learning Points

A resurfaced compartment with an uncorrected alignment treated the surface and left the mechanics.
A deficient meniscus produces the same failure through a different route.
Symptoms that never matched the compartment mean an incidental finding was treated.
A large defect in a well aligned knee with an intact meniscus is the best case for resurfacing.
Attribution to a single injury needs an acute mechanism and early imaging.

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.