Posterior Knee Palpation

For Medical Students

What It Tests

Palpating the back of the knee tests the structures nothing else in the examination reaches: the posterior joint line, the hamstring tendons, the posteromedial and posterolateral corners, and the contents of the popliteal fossa. 2.9.4 covers the posteromedial corner.

It is the part of the knee most often omitted, because it requires the patient to be turned or the knee to be flexed and the examiner to change position. 4.6.1 covers the sequence it belongs to.

Several findings live only here: a posterior horn tear's tenderness, a posteromedial corner injury, a popliteal cyst and the hamstring insertions. 4.6.10 covers the fossa itself.

How It Is Performed

With the patient supine and the knee flexed to about ninety degrees, reach behind the knee with both hands and palpate the posterior joint line medially and laterally.

Palpate the hamstring tendons at the back of the thigh, following them to their insertions, and distinguish the medial group from the biceps laterally. 4.6.8 covers the fibular head.

Palpate the posteromedial corner, behind the medial collateral ligament's course and above the joint line. 4.12.5 covers the structure there.

Turn the patient prone if a thorough posterior examination is needed, which is also the position for the dial test. 4.13.5 covers that test.

Stand the patient up and look at the back of the knee with the knee extended, which is how a popliteal cyst is best seen. 4.6.10 covers it.

What a Positive Means

Posteromedial joint line tenderness suggests a posterior horn tear of the medial meniscus, which is the commonest useful finding here. 4.6.4 covers joint line tenderness.

Tenderness in the posteromedial corner behind the collateral's course suggests a posteromedial corner injury, which is the finding that makes a medial injury surgical. 4.12.5 covers it.

A palpable swelling in the fossa indicates a cyst or a mass, and the two are distinguished by whether it changes with knee position. 4.6.10 covers the examination.

Tenderness along a hamstring tendon indicates a tendon problem rather than a joint one, and it is frequently referred to the knee. 4.6.6 covers tendon tenderness.

Pulsation in the fossa is the popliteal artery, and an expansile pulsatile mass is an aneurysm, which is a different and urgent diagnosis. 4.6.10 covers it.

MRCS Level

How It Is Performed

In a viva reaching behind the knee is a visible demonstration of completeness, and candidates who do it stand out because so few do.

The expected points are the flexed knee, the posterior joint line medially and laterally, the hamstrings, the posteromedial corner, the prone position if needed, and the standing view of the fossa.

Say that you would examine the fossa with the knee extended and the patient standing, because that is when a cyst is most apparent. 4.6.10 covers it.

Say that you would feel for the popliteal pulse, which is both part of the vascular examination and a landmark. 4.11.7 covers the vascular assessment.

Say that you would use the prone position for the dial test and take the posterior palpation at the same time, which is efficient and makes the examination more likely to happen. 4.13.5 covers the test.

What a Positive Means

The reasoning expected is that the posterior horns of both menisci and the posterior capsular structures lie behind the joint's mid coronal plane, so they are only accessible from behind. 2.5.7 covers root attachments.

The posteromedial corner's structures are deep and posterior to the collateral ligament, which is why their tenderness sits in a specific place and why palpating the collateral's course misses them. 2.9.3 covers the posterior oblique ligament.

A popliteal cyst communicates with the joint through a valve like opening, which is why it fills with an effusion and empties variably, and why its size changes with knee position. 4.8.8 covers chronic effusions.

The popliteal artery and the tibial nerve lie in the fossa, which is why a mass there can produce distal symptoms and why the examination extends to the foot. 4.11.7 covers it.

How Good It Is

Posterior palpation is reliable for a palpable mass and a tender posterior joint line, and unreliable for anything subtle, because the structures are deep and the access is awkward.

Its value is almost entirely in finding things nothing else looks for, which makes its omission the real cost rather than its accuracy.

It is harder in an obese patient and in a knee that cannot be flexed, and in both the standing inspection carries more weight. 4.23.4 covers those patients.

Imaging identifies the posterior structures far better, and this is one of the clearer cases in the palpation chapter where imaging is the stronger tool. 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 the posterior examination contributes two things that change plans and one that changes pathways.

The first is posteromedial corner tenderness, which contributes to whether a medial injury is treated surgically. 4.12.5 covers the structure.

The second is posterior horn and root tenderness, which contributes to the decision about a repair rather than a resection. 4.9.9 covers meniscal root tears.

The third is a popliteal mass, which moves the patient to vascular or oncological assessment depending on what it is, and that change of pathway is the most consequential thing on this page. 4.6.10 covers it.

In the multiligament knee the posterior examination is part of the sequence and the popliteal pulse is part of the urgent assessment. 4.11.7 covers it.

Where It Misleads

The commonest error is omitting it, which is a choice made by not changing position.

The second is palpating the posterior joint line with the knee extended, where nothing is accessible.

The third is reading posterior tenderness as a hamstring problem without examining the joint line, or the reverse.

The fourth is examining a popliteal mass supine only, where a cyst may not be apparent.

The fifth is not feeling for a pulse, which is both a landmark and a safety check.

Fellowship Level

Where It Misleads

In referred practice the posterior examination is the part that has not been done, and doing it answers a proportion of referrals outright.

A patient with posteromedial pain, a normal anterior examination and normal imaging of the anterior structures has often had the posterior half of the assessment omitted at every visit. 4.6.4 covers the joint line.

A patient with a persisting posteromedial complaint after a medial reconstruction has an unaddressed posteromedial corner, and the tenderness sits behind the collateral's course. 4.12.8 covers that assessment.

A patient with a popliteal mass that was called a cyst and is not changing with knee position needs imaging rather than reassurance, since a solid mass behaves differently. 4.6.10 covers the examination.

A patient with distal symptoms and a popliteal mass has a compressive lesion, and the examination extends to the foot rather than stopping at the fossa. 4.11.7 covers it.

In medicolegal work the absence of any recorded posterior examination is common and is a reasonable criticism of a record, because several diagnoses live only there. 4.23.7 covers that setting.