Rotational Alignment

For Medical Students

What It Tests

Rotational alignment is the orientation of the femur and the tibia about their long axes, and it determines where the knee points when the foot is forwards.

It matters in a knee examination because an internally rotated femur or an externally rotated tibia changes the patella's path and the knee's loading without any abnormality at the joint itself. 2.4.4 covers patellar tracking.

It is invisible in a front on inspection of the knee alone, which is why it is a separate assessment rather than part of the coronal one. 4.5.1 covers the coronal axis.

How It Is Performed

Lay the patient prone with the knees flexed to ninety degrees and the feet upwards.

Assess femoral rotation by rotating each hip internally and externally and comparing the ranges, since increased internal rotation with reduced external rotation suggests femoral anteversion.

Assess tibial rotation by looking at the thigh foot angle: the angle between the axis of the thigh and the axis of the foot, with the ankle in neutral.

Compare both sides and record both figures, since the comparison is the finding. 4.1.8 covers the record.

Stand the patient up and look at where the patellae point with the feet forwards, which is the functional version of the same assessment. 4.3.3 covers standing alignment.

What a Positive Means

Increased hip internal rotation with reduced external rotation suggests femoral anteversion, which turns the knee inwards when the foot is forwards.

An increased thigh foot angle indicates external tibial torsion, and a reduced or negative one indicates internal torsion.

The combination of femoral anteversion and external tibial torsion is the classic malrotation pattern associated with patellofemoral complaints, and the knee itself is usually normal. 4.2.1 covers pain.

A unilateral rotational abnormality after a fracture or an osteotomy is acquired, and the operation notes and imaging are needed to interpret it. 4.3.7 covers surgical scars.

Rotational alignment also affects the dial test, since the thigh foot angle is the measurement that test compares. 4.13.5 covers the dial test.

MRCS Level

How It Is Performed

In a viva this is the assessment that distinguishes a candidate who examines a limb from one who examines a joint, and the prone position is the giveaway.

The expected points are the prone position with the knees at ninety degrees, the hip rotation comparison, the thigh foot angle, both sides, and the standing observation.

Say that you would examine the hip, since femoral rotation is a hip measurement and the knee complaint may be secondary to it. 4.4.5 covers a related pattern.

Say that the clinical measurements are estimates and that computed tomography measures rotation where a plan depends on it. 4.1.6 covers that relationship.

Say that rotational malalignment is a cause of patellofemoral pain and instability rather than of ligament failure, which keeps the finding in its proper place. 2.4.4 covers tracking.

What a Positive Means

The reasoning expected is that the quadriceps pulls along the femur and the patellar tendon inserts on the tibia, so the angle between those two bones in rotation determines the lateral vector on the patella. 2.4.3 covers patellar biomechanics.

Femoral anteversion internally rotates the trochlea under the patella, and external tibial torsion moves the tubercle laterally, and both increase that vector. 2.4.4 covers tracking.

Rotation also alters the knee's loading in gait, since a knee pointing inwards under load is functionally in valgus. 3.13.7 covers dynamic alignment.

The thigh foot angle is the measurement the dial test compares between sides, so an asymmetrical baseline torsion makes that test harder to interpret. 3.10.7 covers the dial test biomechanics.

How Good It Is

Clinical rotational assessment is a reasonable screen and a poor measurement, and computed tomography is the measurement where one is needed.

The thigh foot angle is the more reproducible of the two clinical assessments, and femoral rotation assessed through hip range is the less so.

The assessment is most valuable in patellofemoral complaints and least valuable in ligament assessment, where its main role is as a caveat on the dial test. 4.13.5 covers it.

It is frequently not performed at all, which is why malrotation presenting as knee pain is a recognised diagnostic delay. 4.2.15 covers referred pain.

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 rotational alignment decides whether a patellofemoral problem is treated at the soft tissue level or with a bony rotational correction, and that is a large difference.

A patient with marked malrotation and recurrent patellar instability may need a rotational osteotomy rather than a soft tissue stabilisation, and the examination raises that question. 2.4.4 covers tracking.

In ligament assessment the finding is a caveat rather than a decision, but a consequential one: an asymmetrical thigh foot angle makes the dial test unreliable and the measurement must be baselined. 4.13.5 covers it.

After a tibial osteotomy or a fracture, rotational malalignment is acquired and is a recognised cause of persisting pain that no ligament surgery addresses. 4.5.1 covers the measurement.

In a knee with persisting symptoms and a normal ligament examination the rotational assessment is one of the few remaining things worth doing. 4.2.15 covers referred pain.

Where It Misleads

The commonest error is not performing it, which is a choice made by examining supine only.

The second is treating the clinical figures as measurements.

The third is attributing a patellofemoral complaint to the knee when the rotation is the cause.

The fourth is interpreting a dial test against the other leg in a patient whose baseline torsion is asymmetrical. 4.13.5 covers it.

The fifth is planning a rotational correction on clinical figures alone.

Fellowship Level

Where It Misleads

In referred practice rotational malalignment is the diagnosis that was not considered, and the patient has usually had several operations that could not have helped.

A patient with recurrent patellar instability, several soft tissue procedures and marked femoral anteversion has a bony problem treated repeatedly as a soft tissue one. 2.4.4 covers tracking.

A patient with persisting pain after a tibial osteotomy may have a rotational malunion that no further soft tissue surgery addresses, and the computed tomography rather than the examination settles it. 4.1.6 covers that relationship.

A patient whose dial test is abnormal and whose corner is intact may have an asymmetrical baseline torsion, and that is a false positive with real consequences if it leads to a corner reconstruction. 4.13.5 covers the test.

In a knee with a rotational deformity and a ligament injury the reconstruction is tensioned in an abnormal rotational position, which is a reason to correct the rotation first in the severe cases. 3.10.8 covers reconstruction biomechanics.

In medicolegal work rotational alignment is almost never recorded before an injury or an operation, which makes attribution of an acquired malrotation difficult unless imaging exists. 4.23.7 covers that setting.