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OCD

Page 4.19.5 · Paediatric Knee Examination · examination page

Osteochondritis dissecans in the growing knee, where the examination is looking for a lesion it cannot feel in a patient who may not localise it.

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OCD

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For Medical Students

What It Tests

In a child or adolescent the lesion presents as vague activity related knee pain, sometimes an effusion after sport, and occasionally a mechanical symptom. 4.17.4 covers the adult presentation.

The examination is deciding whether the pain is articular, where the loaded compartment is, and whether anything suggests the fragment has separated. 4.17.2 covers mechanical symptoms.

It matters that the paediatric version behaves differently from the adult one, because growth gives a stable lesion a chance to heal. 4.19.1 covers the growth plate assessment.

How It Is Performed

Take the history: the age, the sport, how long the pain has been present, and whether it is worse during or after activity. 4.2.11 covers aggravating factors.

Ask specifically about catching, locking and giving way, since those are the clinical markers of an unstable fragment. 4.2.5 covers locking.

Assess the effusion, because a recurrent effusion after sport is often the only objective finding. 4.8.3 covers the bulge sign.

Palpate the femoral condyles with the knee flexed, since the commonest site only becomes accessible in flexion. 4.6.1 covers systematic palpation.

Measure the range and note any block or any pain at a particular angle. 4.7.6 covers the painful arc.

Assess the gait, since a child with a condylar lesion may walk with the limb externally rotated. 4.4.1 covers normal gait.

Examine the other knee, because the lesion is bilateral in a proportion of cases. 4.1.4 covers the structured approach.

What a Positive Means

Activity related pain with a recurrent effusion and tenderness over a femoral condyle in flexion is the characteristic picture.

A mechanical symptom with those findings suggests the fragment is unstable or separated, which changes the urgency. 4.17.2 covers mechanical symptoms.

A block to full extension suggests a loose fragment within the joint. 4.5.4 covers the flexion deformity.

Tenderness in flexion over the lateral aspect of the medial condyle fits the commonest site, and a normal joint line argues against a meniscal cause. 4.6.4 covers joint line tenderness.

A normal examination in a child with activity related pain is common and does not exclude the lesion. 4.1.6 covers that relationship.

Key Learning Points

  • The presentation is vague activity related pain rather than a clear mechanical story.
  • Catching, locking and giving way are the clinical markers of instability.
  • The commonest site is only accessible with the knee flexed.
  • A block to extension suggests a loose fragment.
  • A normal examination does not exclude the lesion.

MRCS Level

How It Is Performed

In a viva this is the adolescent with activity related knee pain and the expected answer reaches skeletal maturity and fragment stability quickly.

The expected points are the age and maturity, the activity history, the mechanical questions, the effusion, the condylar palpation in flexion, the range, the gait and the other knee.

Say that you would palpate the condyles in flexion and give the reason. 4.6.1 covers systematic palpation.

Say that the examination raises the diagnosis and that the imaging grades the lesion. 4.1.6 covers that relationship.

Say that you would examine both knees, since the condition can be bilateral. 4.19.6 covers developmental variants.

What a Positive Means

The reasoning expected is that the lesion starts in the subchondral bone, so the overlying cartilage loses its support and can separate with it. 3.5.1 covers contact areas.

A lesion that stays attached can revascularise while growth continues, which is why skeletal maturity governs the prognosis. 4.19.1 covers the growth plate assessment.

A separated fragment becomes a loose body and produces the mechanical symptoms, so the history is the clinical proxy for stability. 4.17.2 covers mechanical symptoms.

The commonest site is loaded in flexion rather than extension, which is why the pain is activity related and why the arc localises it. 3.5.4 covers the effects of flexion.

How Good It Is

The examination raises the diagnosis in an adolescent with the characteristic history and cannot grade the lesion.

Its most useful contribution is the mechanical history, because stability is the decision the treatment turns on. 4.17.2 covers mechanical symptoms.

It is insensitive for a stable lesion, which may produce only an effusion and vague pain.

Magnetic resonance imaging grades stability and radiographs show the lesion, so the examination's role is the referral. 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 lesion starts in the subchondral bone and the cartilage loses its support.
  • An attached lesion can revascularise while growth continues.
  • A separated fragment becomes a loose body and produces mechanical symptoms.
  • The commonest site is loaded in flexion, which is why the pain is activity related.
  • The examination's contribution is the mechanical history and the referral.

FRCS Level

How Good It Is

At decision level the lesion is sorted by skeletal maturity and by stability, and the examination establishes the first and contributes to the second.

A stable lesion in a skeletally immature knee is observed and protected, and the examination's job is confirming that no mechanical symptom is present. 4.17.2 covers mechanical symptoms.

An unstable or detached lesion moves towards intervention, and the mechanical history is what raises it. 4.20.5 covers the cartilage surgery assessment.

A lesion in a near mature knee behaves like the adult version, so the maturity assessment changes the expected course rather than the diagnosis. 4.17.4 covers the adult version.

Alignment is assessed, because a malaligned limb loads the affected compartment and changes the plan. 4.5.1 covers the mechanical axis.

Where It Misleads

The commonest error is attributing an adolescent's knee pain to growth or to overuse without examining for an effusion. 4.8.3 covers the bulge sign.

Condylar tenderness is missed when the knee is palpated in extension. 4.6.1 covers systematic palpation.

A mechanical symptom reported by a child is unreliable, and the parent's account and the patient's differ. 4.2.5 covers locking.

An effusion is attributed to activity when it is the only sign of an articular lesion. 4.8.9 covers synovitis.

A bilateral finding is read as a normal variant because it is symmetrical. 4.19.6 covers developmental variants.

Key Learning Points

  • Attributing adolescent knee pain to growth without examining for an effusion is the commonest error.
  • Condylar tenderness is missed when the knee is palpated in extension.
  • A child's report of a mechanical symptom is unreliable.
  • An effusion may be the only sign of an articular lesion.
  • A symmetrical bilateral finding is not thereby normal.

Fellowship Level

Where It Misleads

At fellowship level the examination cannot answer the question the treatment turns on, which is whether the fragment is stable.

The mechanical history is the clinical proxy for stability and it is an imperfect one, because a stable lesion can catch and an unstable one can be silent. 4.17.2 covers mechanical symptoms.

Skeletal maturity governs the prognosis and the clinical assessment of maturity is approximate, so the imaging carries that question too. 4.19.1 covers the growth plate assessment.

A healed lesion can leave a residual contour abnormality that remains tender without being active, and the examination does not separate the two. 4.17.5 covers articular cartilage defects.

Pain from the lesion and pain from the altered loading around it are not separable clinically, and only the second responds to alignment correction. 3.5.6 covers the effects of malalignment.

Repeated examination over time is more informative than any single assessment here, which makes the record the useful instrument rather than the findings. 4.1.4 covers the structured approach.

Key Learning Points

  • The mechanical history is an imperfect proxy for fragment stability.
  • Clinical assessment of skeletal maturity is approximate.
  • A healed lesion can remain tender without being active.
  • Pain from the lesion and from the altered loading are not separable clinically.
  • Repeated examination over time beats any single assessment.

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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