Quadriceps Tendon

For Medical Students

What It Shows

The quadriceps tendon is formed from several layers contributed by the different quadriceps components, inserting on the patella. 2.4.5 covers the patellar surgical relevance.

Ultrasound resolves those layers, which no routine magnetic resonance sequence does as clearly. 5.5.10 covers the tendons.

It matters because a partial tear is a tear of one or more layers, and naming the layer is the useful part of the report. 5.4.6 covers the patellar tendon.

How It Is Acquired

Scan in long axis with the knee slightly flexed, which tensions the tendon. 5.4.1 covers the anterior knee.

Identify the layers, which appear as parallel bright bands separated by thin dark lines. 5.2.8 covers reflection.

Keep the beam perpendicular, because the layers are parallel fibred and anisotropic. 5.2.10 covers anisotropy.

Scan to the insertion and the suprapatellar region, since the insertion is where rupture occurs. 5.4.20 covers tendon procedures.

Examine dynamically by asking for a contraction, which demonstrates continuity functionally. 5.4.15 covers dynamic instability.

What Normal Looks Like

Parallel bright layers with thin dark interfaces between them. 5.2.8 covers reflection.

A uniform thickness along the tendon's length.

A clean insertion on the patellar superior pole. 2.4.1 covers the patellar anatomy.

No colour Doppler signal in the tendon substance. 5.2.11 covers Doppler imaging.

What Abnormal Looks Like

An anechoic cleft in one layer with the others intact, which is a partial tear. 5.5.10 covers the tendons.

Complete discontinuity with a gap and retraction, which is a rupture. 5.3.12 covers patellar fractures.

Focal thickening with loss of the layered pattern, which is tendinopathy. 5.4.6 covers the patellar tendon.

Calcification with acoustic shadowing within the tendon. 5.14.4 covers crystal arthropathy.

MRCS Level

How It Is Acquired

In a viva this is the tendon to name when asked what ultrasound adds over magnetic resonance imaging.

The expected points are the slight flexion, the layers, the perpendicular beam, the insertion, and the dynamic contraction.

Say that the layer involved is what the report should name. 5.5.10 covers the tendons.

Say that a dynamic contraction tests continuity. 5.4.15 covers dynamic instability.

Say that anisotropy is the commonest reason a normal layer looks torn. 5.2.10 covers anisotropy.

What Abnormal Looks Like

The reasoning expected is that each layer comes from a different muscle, so a tear of one layer leaves the others transmitting force and the patient still extending. 2.4.5 covers the patellar surgical relevance.

That is why a partial tear can present with a functional knee, and why extension power does not exclude one. 4.7.8 covers the extension lag.

A complete rupture leaves no layer intact, so the clinical deficit is immediate and the ultrasound confirms rather than discovers it. 4.7.1 covers active motion.

The layered structure is also why anisotropy is so troublesome here: an oblique beam darkens one layer and imitates exactly the finding being looked for. 5.2.10 covers anisotropy.

How Good It Is

Ultrasound is the best modality for the quadriceps tendon's internal structure and for demonstrating its continuity dynamically.

Its best contribution is the layer by layer partial tear assessment, which no other routine study gives. 5.5.10 covers the tendons.

It is limited by anisotropy imitating the finding, and by the difficulty of distinguishing a high grade partial tear from a complete one. 5.2.10 covers anisotropy.

No figures appear for accuracy on this page, under decision 028, and no tendon thickness values appear either: those are published quantities and this environment cannot check them.

FRCS Level

How Good It Is

At decision level the question is whether the extensor mechanism needs repairing, and the ultrasound contributes the structural half.

A complete rupture is an operative decision made clinically, and the imaging adds the level and the retraction. 4.7.8 covers the extension lag.

A high grade partial tear in a functioning knee is the genuinely difficult case, and the layer assessment is what informs it. 5.5.10 covers the tendons.

A dynamic examination showing the tendon failing to transmit a contraction is functional evidence no static study gives. 5.4.15 covers dynamic instability.

Tendinopathy without a tear is a loading question rather than a surgical one, and the boundary belongs to Section 6. 5.4.20 covers tendon procedures.

Where It Misleads

The commonest error is reporting anisotropy as a partial tear. 5.2.10 covers anisotropy.

A slack tendon is reported as thickened. 5.4.1 covers the anterior knee.

A high grade partial tear is reported as complete, or the reverse. 5.5.10 covers the tendons.

The layer involved is not named, which removes the report's usefulness. 5.20.1 covers structured reporting.

Operative indication is taken from the ultrasound rather than the examination. 4.7.1 covers active motion.

Fellowship Level

Where It Misleads

At fellowship level the quadriceps tendon is where ultrasound's advantage is clearest and its reporting weakest.

The layer level description is genuinely superior to a routine magnetic resonance study and almost never appears in a report, so the advantage is realised only when the surgeon scans. 5.20.1 covers structured reporting.

Distinguishing a high grade partial tear from a complete one changes the operation and is the hardest call ultrasound makes here, with no established criterion. 5.5.10 covers the tendons.

The dynamic contraction test is the most informative manoeuvre available and is not recorded in any transferable form. 5.4.15 covers dynamic instability.

Published accuracy for these tears reflects the operators in the study, which is the general ultrasound caveat and bites hardest where the call is close. 5.21.1 covers the meniscal imaging literature.

The useful practice is to name the layers, state whether a contraction transmitted, and say who scanned. 5.2.6 covers sound waves.