POL Injuries

For Medical Students

What It Shows

The posterior oblique ligament is the posterior part of the medial capsule, running obliquely from the femur to the tibia behind the superficial ligament. 2.9.3 covers the posterior oblique ligament.

It appears on posterior coronal images, blending with the capsule and the semimembranosus. 2.9.5 covers the semimembranosus.

It matters because it restrains rotation as well as valgus, so its injury changes the knee from one that heals to one that may not. 3.9.5 covers the POL function.

How It Is Acquired

Assess it on posterior coronal and axial images. 5.5.2 covers the sports knee protocol.

Trace it from the femur to the tibia behind the superficial ligament. 2.9.3 covers the posterior oblique ligament.

Assess the semimembranosus and its attachments, which blend with it. 2.9.5 covers the semimembranosus.

Assess the whole posteromedial corner rather than this structure alone. 5.9.5 covers posteromedial corner injuries.

Assess the cruciates, since combined injury is the usual pattern. 3.9.10 covers the combined ACL and MCL injury.

What Normal Looks Like

A definable oblique band behind the superficial ligament. 2.9.3 covers the posterior oblique ligament.

Continuity with the capsule and the semimembranosus. 2.9.5 covers the semimembranosus.

No oedema in the posteromedial soft tissues. 5.5.9 covers the ligaments.

An intact meniscocapsular junction. 5.6.10 covers ramp lesions.

What Abnormal Looks Like

Loss of definition, or discontinuity of the oblique band. 2.9.3 covers the posterior oblique ligament.

Oedema through the posteromedial soft tissues. 5.5.9 covers the ligaments.

Injury at the femoral origin, which is the common site. 2.9.7 covers the surgical anatomy.

An associated meniscocapsular separation. 5.6.10 covers ramp lesions.

Injury of this structure with an anterior cruciate tear, which is the pattern producing rotatory laxity. 5.9.6 covers the AMRI imaging.

MRCS Level

How It Is Acquired

In a viva the expected answer treats this structure as the decision point.

The expected points are the posterior images, the trace from femur to tibia, the semimembranosus, the whole corner, and the cruciates.

Say that this structure carries rotation. 3.9.2 covers the rotational stability.

Say that its injury with a cruciate tear produces anteromedial rotatory instability. 3.9.7 covers the AMRI biomechanics.

Say that the clinical assessment is specific to it. 4.12.5 covers the POL assessment.

What Abnormal Looks Like

The reasoning expected is that this ligament tightens in extension and lies obliquely, so it restrains the tibia from rotating externally as well as from opening medially, which is the function the superficial ligament does not provide. 3.9.5 covers the POL function.

That makes it the structure whose loss converts a valgus injury into a rotational one. 3.9.2 covers the rotational stability.

Its blending with the capsule makes it hard to define, so oedema in the posteromedial soft tissues is often the only sign. 5.5.9 covers the ligaments.

A meniscocapsular separation commonly accompanies it, because the two sit at the same junction. 5.6.10 covers ramp lesions.

How Good It Is

Magnetic resonance imaging shows the posteromedial soft tissues well and defines this ligament inconsistently.

Its best contribution is the posteromedial oedema pattern and the associated meniscocapsular finding. 5.6.10 covers ramp lesions.

It is limited because the structure blends with the capsule, because chronic injury leaves no oedema, and because the rotational deficit is clinical. 4.12.5 covers the POL assessment.

No figures appear for accuracy on this page, under decision 028, and no laxity values or rotation thresholds appear either: those are clinical grades with published definitions and this environment cannot check them.

FRCS Level

How Good It Is

At decision level this is the medial structure whose injury argues for an operation. 3.9.6 covers the posteromedial corner function.

With a cruciate tear it is repaired or reconstructed at the same operation. 3.9.10 covers the combined ACL and MCL injury.

Left untreated it is a recognised cause of cruciate graft failure. 5.7.11 covers the graft failure.

The meniscocapsular junction is addressed through the same approach. 5.6.10 covers ramp lesions.

Chronic rotatory laxity needs the examination under anaesthesia. 4.12.6 covers the AMRI assessment.

Where It Misleads

The commonest error is omitting this structure because the superficial ligament explained the injury. 5.20.4 covers reporting MCL injuries.

Posteromedial oedema is reported as a superficial ligament sprain. 2.9.1 covers the superficial MCL.

Chronic injury with no oedema is read as normal. 5.5.9 covers the ligaments.

The semimembranosus attachment is reported as a separate tendon finding. 2.9.5 covers the semimembranosus.

Rotational laxity is inferred from the images. 4.12.6 covers the AMRI assessment.

Fellowship Level

Where It Misleads

At fellowship level the cruciate graft has stretched and the medial side was called a sprain. 5.7.11 covers the graft failure.

This structure and the meniscocapsular junction are where that knee's instability came from, and both were visible originally. 5.6.10 covers ramp lesions.

Chronic injury here produces laxity with no imaging finding, so the diagnosis becomes clinical. 4.12.6 covers the AMRI assessment.

A medial reconstruction addresses this ligament's function with a graft that does not reproduce it. 5.9.7 covers the post-operative medial reconstructions.

Alignment belongs in the chronic case, because valgus loads a medial reconstruction. 5.3.6 covers the long leg alignment films.

The useful report names this structure, its site, the posteromedial oedema, the meniscocapsular junction and the cruciates. 5.20.4 covers reporting MCL injuries.