Patellar Tendon, Tendon Examination

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Patellar Tendon

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For Medical Students

What It Tests

The patellar tendon joins the lower pole of the patella to the tibial tubercle, and examining it tests for tendinopathy, for partial tearing and for rupture. 4.6.7 covers the tubercle.

Rupture abolishes active extension, exactly as a quadriceps rupture does, and is diagnosed the same way. 4.16.1 covers the other tendon.

Tendinopathy at its origin is far commoner and is the diagnosis most often missed in an athlete with anterior knee pain. 4.16.3 covers it.

How It Is Performed

Lay the patient supine and look for a high riding patella, which follows a complete rupture, and for a defect below the patella. 4.3.4 covers the sitting assessment.

Palpate the tendon from the lower pole of the patella to the tubercle, with the knee extended and relaxed, noting the exact position of any tenderness. 4.6.6 covers tendon tenderness.

Repeat the palpation with the knee flexed and the tendon under tension, since tenderness changes with tension and both readings are useful.

Ask the patient to extend the knee and then to hold the straight leg lifted, which identifies a rupture. 4.7.1 covers active motion.

Test resisted extension and note whether that reproduces the pain, which localises it to the tendon rather than the joint.

What a Positive Means

A palpable gap below the patella with an inability to hold the leg straight and a high riding patella indicates a complete rupture, and that is urgent.

Focal tenderness at the lower pole of the patella with painful resisted extension indicates tendinopathy at the tendon's origin. 4.16.3 covers it.

Tenderness at the tubercle end indicates an insertional problem, and in an adolescent that is a traction apophysitis. 4.16.4 covers it.

Tenderness in the mid substance is less common and raises a partial tear or a previous graft harvest. 4.20.1 covers that assessment.

Intact active extension with a tender tendon does not exclude a partial tear, which the imaging settles. 4.1.6 covers that relationship.

Key Learning Points

Rupture abolishes active extension and is diagnosed with the straight leg hold.
A high riding patella follows a complete rupture.
Focal tenderness at the lower pole with painful resisted extension is tendinopathy at the origin.
Tenderness at the tubercle end is an insertional problem, and in an adolescent an apophysitis.
Mid substance tenderness raises a partial tear or a previous graft harvest.

MRCS Level

How It Is Performed

In a viva this tendon is usually a route into either the extensor mechanism or the athletic knee, and the position of the tenderness decides which.

The expected points are the patellar height, the palpation of the whole tendon in two positions, the active extension, the straight leg hold, and the resisted extension.

Say that you would palpate at the lower pole specifically, because that is where tendinopathy sits and where it is missed. 4.16.3 covers it.

Say that you would ask about the graft used in any previous cruciate reconstruction, since a bone patellar tendon bone harvest leaves a defect and a tender site. 4.20.1 covers that assessment.

Say that the patellar height is compared with the other knee in the same position, since an absolute impression is unreliable. 4.3.4 covers the sitting assessment.

What a Positive Means

The reasoning expected is that the tendon transmits the whole extensor force, so it fails at its weakest point, which is the enthesis in a young athlete and the insertion in a degenerate tendon. 2.4.3 covers patellar biomechanics.

Tendinopathy at the origin is a load problem of the enthesis, which is why it presents in jumping athletes and responds to load management rather than to surgery. 4.16.3 covers it.

A complete rupture allows the patella to be pulled proximally by the quadriceps, which is the mechanism behind the high riding patella and makes the inspection diagnostic. 2.4.1 covers the patellar anatomy.

A previous graft harvest leaves the tendon's central third reconstituted rather than normal, which is why the examination of a reconstructed knee reads differently. 4.20.1 covers it.

How Good It Is

The clinical diagnosis of a complete rupture is reliable and rests on the straight leg hold, as with the quadriceps tendon. 4.16.1 covers it.

The localisation of tendinopathy is precise and the diagnosis is clinical, which makes this one of the few conditions in the section where the examination is the reference. 4.16.3 covers it.

It cannot separate tendinopathy from a partial tear, which ultrasound and magnetic resonance imaging do. 4.1.6 covers that relationship.

It is unreliable in a knee with a previous graft harvest, where the anatomy and the tenderness are both altered. 4.20.1 covers that assessment.

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 tendon fails at its weakest point: the enthesis in a young athlete, the insertion in a degenerate tendon.
Tendinopathy at the origin is a load problem that responds to load management.
A rupture lets the quadriceps pull the patella proximally, making the inspection diagnostic.
A previous harvest leaves the central third reconstituted rather than normal.
Localisation of tendinopathy is precise, and the diagnosis is clinical.

FRCS Level

How Good It Is

At decision level the examination makes the urgent diagnosis and the tendinopathy diagnosis, and defers the middle ground.

A complete rupture is repaired early, and the examination's job is the diagnosis on the day. 4.7.8 covers the finding.

Tendinopathy is managed by load, and recognising it prevents an arthroscopy for anterior knee pain. 4.16.3 covers it.

A partial tear in an athlete is a decision about load and time rather than about an operation, and the imaging informs it.

In a knee being planned for a cruciate reconstruction the tendon's state is part of the graft choice, and a tendinopathic tendon argues against taking a graft from it. 4.20.1 covers that assessment.

Where It Misleads

The commonest error is not testing active extension in a tender tendon after a sudden load.

The second is palpating only the tender area rather than the whole tendon.

The third is attributing anterior pain to the joint when the lower pole is tender. 4.15.9 covers that alternative.

The fourth is examining the tendon in one position only.

The fifth is comparing patellar height between knees in different positions.

Key Learning Points

The examination makes the urgent diagnosis and the tendinopathy diagnosis.
A tendinopathic tendon argues against taking a graft from it.
Attributing anterior pain to the joint when the lower pole is tender is a common error.
A partial tear in an athlete is a load and time decision.
Patellar height has to be compared in the same position on both sides.

Fellowship Level

Where It Misleads

In referred practice this tendon is most often relevant as a graft donor site or as a tendinopathy that has been investigated as something else.

A patient with tenderness at the lower pole years after a bone patellar tendon bone harvest has donor site pain, which is common, under recognised and not a failure of the reconstruction. 4.20.1 covers that assessment.

A patient with a normal arthroscopy and persisting anterior pain who is tender at the lower pole has a tendinopathy that the arthroscopy could not have addressed. 4.16.3 covers it.

A patient with a rupture after a previous harvest has a tendon that was already altered, and the repair is a different proposition.

A patient with bilateral insertional symptoms and systemic features has an enthesopathy rather than an overload problem, and the specialty changes. 4.2.14 covers inflammatory pain.

In medicolegal work a missed patellar tendon rupture is the same avoidable failure as a missed quadriceps rupture, and the same absent test is usually the reason. 4.23.7 covers that setting.

Key Learning Points

Donor site pain after a graft harvest is common, under recognised and not a reconstruction failure.
A normal arthroscopy with lower pole tenderness is a tendinopathy the arthroscopy could not address.
A rupture after a previous harvest is a different repair proposition.
Bilateral insertional symptoms with systemic features is an enthesopathy.
A missed rupture traces to the same absent test as at the quadriceps tendon.

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.