Hypermobile Patients

For Medical Students

What It Tests

A generally hypermobile patient has more joint range and more passive excursion everywhere, so the ligament tests read positive without a ligament injury. 4.5.5 covers hyperextension.

The examination is distinguishing laxity, which is the patient's normal, from instability, which is a symptom. 4.2.2 covers instability.

It matters because treating laxity as injury leads to an operation that does not help and may not hold. 4.19.4 covers the paediatric patellar instability assessment.

How It Is Performed

Assess generalised hypermobility formally rather than by impression, using the standard multi joint assessment.

Ask about family history, since hypermobility is often familial.

Ask about symptoms separately from findings, because the symptom is what decides whether anything follows. 4.2.2 covers instability.

Examine both knees and several other joints, since the pattern is what establishes generalised laxity. 4.1.4 covers the structured approach.

Record knee hyperextension, which is usually present. 4.7.3 covers hyperextension.

Perform the ligament tests and record the end point as well as the excursion, since a lax ligament still has a firm end point and a torn one does not. 4.10.4 covers the Lachman test.

Record the patellar translation, which is commonly increased. 4.15.4 covers patellar glide.

What a Positive Means

Symmetrical increased excursion with firm end points across several joints is generalised laxity rather than injury.

A soft end point on one side with increased excursion on both is an injury in a lax patient, and the end point is what separates them. 4.10.4 covers the Lachman test.

Symptoms of giving way with symmetrical laxity point at control rather than at structure. 4.2.6 covers giving way.

Increased patellar translation without apprehension is laxity, and with apprehension is instability. 4.15.3 covers the patellar apprehension test.

Knee hyperextension in a hypermobile patient is a finding without being a problem. 4.5.5 covers hyperextension.

MRCS Level

How It Is Performed

In a viva this is the patient whose tests all read positive, and the expected answer separates laxity from instability.

The expected points are the formal hypermobility assessment, the family history, the symptom history, the multi joint examination, the hyperextension, the end point as well as the excursion, and the patellar translation.

Say that you would assess hypermobility formally. 4.1.4 covers the structured approach.

Say that you would record the end point, and give the reason. 4.10.4 covers the Lachman test.

Say that symptoms decide whether a finding matters. 4.2.2 covers instability.

What a Positive Means

The reasoning expected is that a ligament's restraint has a length and a stiffness, and hypermobility changes the length while leaving a firm end point. 3.7.2 covers the primary restraints.

A torn ligament removes the end point, which is why the quality of the stop rather than the distance is the diagnostic feature. 4.7.5 covers the end feel.

Reduced passive restraint raises the share carried by muscle control, which is why rehabilitation is the first treatment in this group. 3.7.3 covers the secondary restraints.

A reconstruction in a lax patient is held by tissue with the same properties, which is why the result differs from a reconstruction in a stiff one. 4.20.1 covers the reconstruction assessment.

How Good It Is

The examination is reliable for establishing generalised laxity and unreliable for grading injury within it.

Its best contribution is the end point, which survives the laxity that defeats the excursion measurement. 4.7.5 covers the end feel.

It is prone to false positives on every laxity test, which is the defining problem of this group.

Imaging shows ligament integrity and is therefore more valuable here than in a patient with normal laxity. 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.

FRCS Level

How Good It Is

At decision level hypermobility changes the indication, the procedure and the expected result.

Symptomatic instability with generalised laxity is treated with rehabilitation first, and the examination establishes which it is. 4.2.6 covers giving way.

A reconstruction in a hypermobile patient has a different expected course, which is part of the consent rather than a surprise afterwards. 4.20.1 covers the reconstruction assessment.

Patellar instability with hypermobility and no bony abnormality is a different problem from patellar instability with dysplasia. 4.15.8 covers trochlear dysplasia.

Bilateral symmetrical findings in a symptomatic patient still need a cause, and hypermobility is one rather than the end of the assessment. 4.1.4 covers the structured approach.

Where It Misleads

The commonest error is reading symmetrical laxity as bilateral injury. 4.1.4 covers the structured approach.

The excursion is recorded and the end point is not. 4.7.5 covers the end feel.

Hypermobility is assessed by impression rather than formally, so it is missed in the mildly affected.

A finding is treated because it is abnormal rather than because it is symptomatic. 4.2.2 covers instability.

The expected result of an operation is quoted from a population without this feature. 4.22.8 covers the use of these scores.

Fellowship Level

Where It Misleads

At fellowship level this group breaks the examination's central assumption, which is that the excursion means something absolute.

Every laxity grade is defined against a normal that this patient does not have, so the grades are uninterpretable and the end point carries the whole assessment. 4.7.5 covers the end feel.

The contralateral comparison fails, because both sides are lax, which removes the examination's usual fallback. 4.1.4 covers the structured approach.

Hypermobility is a spectrum assessed by a scored test whose threshold is a convention, so a patient just below it is not thereby normal. 4.5.5 covers hyperextension.

Connective tissue disorders sit at the far end of the spectrum and change the surgical risk as well as the laxity, and the knee examination does not identify them. 4.3.6 covers skin changes.

Symptomatic instability in a lax patient can be a control problem, a structural problem or both, and the examination cannot apportion it. 4.2.2 covers instability.