Torsional Assessment

For Medical Students

What It Tests

Torsion is the twist along the femur and the tibia, and it determines where the foot points and how the knee is loaded during gait. 4.5.6 covers rotational alignment.

The examination is measuring the rotation at each level separately, because femoral and tibial torsion can add to each other or cancel out. 4.4.1 covers normal gait.

It matters because in toeing, out toeing and apparent knock knees are commonly torsional rather than angular. 4.19.6 covers developmental variants.

How It Is Performed

Watch the child walk and note the angle the foot makes with the line of progression. 4.4.1 covers normal gait.

Assess hip rotation with the patient prone and the knees flexed, comparing internal with external rotation. 4.5.6 covers rotational alignment.

Assess the thigh foot angle with the patient prone, which measures the tibial component. 4.5.6 covers rotational alignment.

Look at the foot itself, since forefoot shape contributes to the foot progression angle. 4.3.1 covers observation from the door.

Look at the patellae while the child walks, since inward facing patellae with outward facing feet is the combined pattern. 4.15.1 covers patellar tracking.

Record the coronal alignment separately, so the two planes are not confused. 4.3.3 covers standing alignment.

Compare the two limbs, because asymmetry changes the interpretation. 4.1.4 covers the structured approach.

What a Positive Means

Increased internal hip rotation with reduced external rotation indicates increased femoral torsion, which turns the whole limb inwards.

An inward thigh foot angle indicates internal tibial torsion, which turns the foot inwards below a normally oriented knee. 4.5.6 covers rotational alignment.

Internally facing patellae with normally facing feet indicates femoral torsion compensated by tibial torsion, which is the pattern a foot progression angle hides. 4.15.1 covers patellar tracking.

Torsion combined with a valgus alignment increases the lateral force on the patella, which links this examination to patellar instability. 3.12.6 covers the Q angle.

Asymmetrical torsion is less likely to be developmental and more likely to follow a growth disturbance or a fracture. 4.19.1 covers the growth plate assessment.

MRCS Level

How It Is Performed

In a viva this is the in toeing child or the maltracking adolescent and the expected answer measures each level rather than describing the gait.

The expected points are the foot progression angle, the prone hip rotation, the thigh foot angle, the foot shape, the patellar orientation during gait, the coronal alignment, and the comparison between limbs.

Say that you would examine prone, since that is the position in which the rotational profile is measured. 4.5.6 covers rotational alignment.

Say that you would separate the femoral from the tibial component, and explain why the foot progression angle alone cannot. 4.4.1 covers normal gait.

Say that you would record the coronal alignment separately. 4.3.3 covers standing alignment.

What a Positive Means

The reasoning expected is that the foot progression angle is the sum of the femoral, tibial and foot contributions, so a normal sum can hide two abnormal parts. 4.5.6 covers rotational alignment.

Femoral torsion rotates the whole knee, so the patella points inwards and the extensor mechanism acts at an angle to the groove. 3.12.6 covers the Q angle.

Tibial torsion rotates the foot below the knee, so the patella is unaffected and the loading of the knee still changes. 3.5.6 covers the effects of malalignment.

Developmental torsion follows an expected course during growth, which is why the age and the trend matter more than the single measurement. 4.19.6 covers developmental variants.

How Good It Is

The clinical rotational profile is reproducible enough to be useful and imprecise as a measurement.

Its best contribution is separating the femoral from the tibial component, which no gait observation does. 4.4.1 covers normal gait.

It is operator dependent, since the prone measurements depend on the end point chosen.

Cross sectional imaging measures torsion properly, so the examination decides whether that is needed. 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 torsion is assessed because it changes what a coronal correction achieves and because it contributes to patellar instability.

A maltracking patella with increased femoral torsion is a different problem from one with a normal rotational profile, and the examination finds the difference. 4.19.4 covers patellar instability.

A valgus knee with a torsional component is not fully described by its coronal deformity, so the assessment is done before any correction is planned. 4.18.4 covers the valgus worn knee.

A varus knee with a torsional component raises the same issue in the opposite direction. 4.18.3 covers the varus worn knee.

Asymmetrical torsion after a physeal injury or a fracture is a separate problem from developmental torsion, and the history separates them. 4.19.1 covers the growth plate assessment.

Where It Misleads

The commonest error is accepting a normal foot progression angle as a normal rotational profile. 4.4.1 covers normal gait.

The prone measurements are operator dependent, so a change between two visits may be the examiner rather than the child. 4.5.6 covers rotational alignment.

Torsion is omitted entirely from the assessment of a deformity, so a coronal correction is planned against an incomplete description. 4.3.3 covers standing alignment.

Foot shape contributes to the foot progression angle and is attributed to the tibia. 4.3.1 covers observation from the door.

Hip pathology changes the available rotation and is read as torsion. 4.2.15 covers referred pain.

Fellowship Level

Where It Misleads

At fellowship level torsion is the part of alignment the examination describes worst and the part a correction most often ignores.

The clinical measurements estimate rotation at two levels and the real geometry is continuous along the bone, so the estimate locates the twist only approximately. 4.5.6 covers rotational alignment.

Compensating femoral and tibial torsion produces a normal gait with an abnormal limb, and correcting one component alone unmasks the other. 4.4.1 covers normal gait.

Rotational and coronal deformity interact, so the clinical description of either one in isolation misstates the load the knee carries. 3.5.6 covers the effects of malalignment.

Torsion's contribution to patellar instability is one of several, and the examination cannot apportion it against the trochlear shape or the soft tissue restraint. 4.15.8 covers trochlear dysplasia.

Soft tissue contracture around a torsional deformity limits the measurement itself, so the finding and the limitation are recorded together. 4.7.5 covers the end feel.