LCL Assessment

For Medical Students

What It Tests

The lateral collateral ligament runs from the lateral femoral epicondyle to the head of the fibula as a discrete cord, outside the joint capsule.

Being a cord rather than a sheet, it can be palpated directly, which no other major knee ligament allows. 3.10.3 covers its function.

Assessing it therefore has two parts that most ligament assessments do not have: feeling whether the structure is there and under tension, and testing how far the joint opens without it. 4.13.1 covers the stress test.

How It Is Performed

Place the leg in the figure of four position. Flex the knee, externally rotate the hip and rest the ankle of the affected leg on the opposite shin.

That position tightens the ligament, and it stands out as a cord across the lateral side of the knee.

Follow it with a finger from the lateral femoral epicondyle down to the fibular head, noting tenderness and whether the cord is palpable along its length.

Compare with the other knee in the same position, because the prominence of the cord varies between people.

Then perform varus stress at thirty degrees and in extension, with your fingers on the lateral joint line. 4.13.1 covers that test.

What a Positive Means

An absent or non palpable cord in the figure of four position, where the other side has one, indicates a disrupted ligament.

Tenderness along the cord with a palpable, tense structure and no increased varus opening is a sprain, which is treated as pain rather than instability.

Increased varus opening at thirty degrees with a soft endpoint indicates a complete injury.

Tenderness localised to the fibular head raises the question of an avulsion with a bone fragment, which changes the treatment and is a radiographic finding. 4.1.6 covers the relationship with imaging.

A disrupted ligament should prompt examination of the common peroneal nerve, which lies just behind the fibular neck. 4.11.7 covers the sequence.

MRCS Level

How It Is Performed

In a viva the figure of four position is the answer, and describing varus stress without it is an incomplete assessment of this structure.

The expected points are the position, following the cord from epicondyle to fibular head, the comparison, and then the varus stress at both angles.

Say that you would examine the fibular head and neck specifically, because an avulsion and a nerve injury both live there.

Say that the ligament is extracapsular, which is why an isolated injury to it produces little effusion and why a tense haemarthrosis points elsewhere. 4.2.3 covers swelling.

Say that you would perform the dial test, since the structures that matter most laterally resist rotation rather than varus and this ligament is the lesser part of the corner. 4.13.5 covers it.

What a Positive Means

The reasoning expected is that the ligament is the principal varus restraint through mid flexion and contributes less in extension, where the cruciates and capsule share it. 3.10.1 covers varus stability.

It also contributes to external rotation restraint, which is why a complete injury increases the dial test and why the corner is assessed as a unit rather than structure by structure. 3.10.6 covers the corner.

Its extracapsular position means an isolated injury heals poorly, because there is little to hold the ends in apposition, which is the anatomical reason the lateral side behaves differently from the medial. 3.10.3 covers its function.

An avulsion from the fibular head with a fragment heals differently again, because the repair is bone to bone rather than ligament to ligament.

How Good It Is

Palpation in the figure of four position is the most specific finding in the lateral examination, because an absent cord is hard to produce any other way.

It is less sensitive than it is specific. A partial injury, or a complete one in a heavy limb, can leave a palpable structure.

Varus stress adds grading and does not add localisation, because it cannot tell this ligament from the rest of the corner. 4.13.1 covers that limitation.

The combination of palpation and the dial test is more informative than varus stress on its own, and that is the practical conclusion of this page.

No figures appear for any of these comparisons, under decision 023, and the comparison is the claim being made.

FRCS Level

How Good It Is

At decision level the palpation finding contributes to whether the lateral side is reconstructed and the corner assessment decides what is reconstructed.

An isolated complete collateral injury is uncommon, and when it is genuinely isolated it is still usually reconstructed rather than braced, because the structure does not heal in a useful position.

A fibular head avulsion with a fragment is the one lateral injury with a straightforward repair, and recognising it from the tenderness and the radiograph changes the operation.

In the combined injury the collateral is reconstructed as part of the corner rather than as a decision of its own, and the examination's contribution is to confirm it is gone. 4.13.8 covers combined injuries.

Alignment is assessed in every case, because a varus limb will stretch any lateral reconstruction and that is the commonest reason one fails.

Where It Misleads

The commonest error is not using the figure of four position, which discards the only direct palpation available in the knee.

The second is reading a palpable cord as an intact corner. The cord is the smaller part of the lateral problem.

The third is attributing lateral pain to the ligament when the structure is tense and non tender on the other side too, which is normal variation.

The fourth is missing a fibular head avulsion, which is a radiographic finding the examination should ask for rather than exclude.

The fifth is finding a disrupted ligament and not examining the nerve.

Fellowship Level

Where It Misleads

In referred practice this ligament is usually intact or already reconstructed, and the examination is answering whether the rest of the corner was addressed.

A reconstructed collateral with a persistent rotational abnormality means the popliteus complex was not reconstructed, and that is the commonest incomplete lateral operation. 4.13.3 covers the popliteus.

A reconstructed collateral in an uncorrected varus limb stretches, and finding it lax at two years with good surgery in the notes usually means the alignment was the missing step.

In a knee with a previous lateral extra-articular tenodesis the lateral soft tissue anatomy is altered and the cord may not be palpable where expected, so an absent cord is less informative. 3.11.7 covers the procedure.

A patient with a healed fibular head avulsion can have a palpable but non functional ligament, because the fragment united in a displaced position and the ligament is slack. The palpation is reassuring and the varus test is not, and the varus test is the one to believe.

In medicolegal work a recorded absent cord is strong evidence of a complete injury at that time, and it is one of the few lateral findings that carries that weight. 4.23.7 covers that setting.