MCQs – Lower Extremity 3

Modern Study Review (AI-Generated)

High-Yield Summary

This topic is a staple of the Royal College exam, focusing heavily on pediatric lower limb deformities, patellofemoral instability, and growth-related fracture patterns. The single most important clinical threshold is the age and degree of deformity dictating surgical intervention, such as osteotomy for Blount’s disease at 5 years with a 30° femoral-tibial angle or genu valgum surgery after age 10 with >10 cm inter-malleolar distance. The examiner often forces a choice between conservative management and surgical correction based on age and severity. While classic exam answers emphasize fixed age cutoffs, modern practice increasingly individualizes timing based on functional impairment and imaging.

High-Yield Decision Matrix

Active Recall Q&A

Blount’s Disease

Q: At what age and femoral-tibial angle should a child with Blount’s disease undergo osteotomy?
A: At 5 years old with a 30° femoral-tibial angle, osteotomy (probably closing wedge) is indicated.
Related Pearl: Recurrence rates are high in this age group; close follow-up is essential, and repeat osteotomies may be necessary.

Patellar Dislocation

Q: What is the initial treatment approach for recurrent patellar dislocations?
A: Start with lateral release followed by vastus medialis advancement (proximal realignment).
Related Pearl: Proximal realignment restores medial patellar stability and balances the extensor mechanism, reducing redislocation risk.

Q Angle

Q: What are the normal Q angle values in males and females?
A: Normal Q angle is about 15°; upper limit is 17° in males and 20° in females.
Related Pearl: Increased Q angle predisposes to patellofemoral pain and instability; sex-specific thresholds guide diagnosis.

Blumensatt’s Line

Q: At what knee flexion angle is Blumensatt’s line visible, and where should the patella be relative to it?
A: At 30° knee flexion; the patella should just cross above Blumensatt’s line.
Related Pearl: This assessment helps diagnose patella alta or baja, which affect knee biomechanics.

Insall Ratio

Q: What is the Insall ratio and its normal threshold?
A: Ratio of patellar tendon length to patella length; tendon should be no more than 1.2 times the patella length.
Related Pearl: A ratio >1.2 indicates patella alta, increasing risk of instability and maltracking.

Genu Valgum

Q: When does genu valgum peak in children, and what is the surgical threshold?
A: Peaks between ages 2-6; surgery considered if valgum persists beyond age 10 with inter-malleolar distance ?10 cm or valgus >15-20°.
Related Pearl: Most cases resolve naturally; premature surgery risks unnecessary intervention and growth plate damage.

Femoral Anteversion + Tibial External Torsion

Q: How should severe femoral anteversion with tibial external torsion in a 9-year-old be managed?
A: Wait until age 10; likely requires double osteotomies (intertrochanteric and supramalleolar).
Related Pearl: Correcting both deformities simultaneously improves gait and reduces recurrence.

Supramalleolar Osteotomy

Q: At what age is supramalleolar osteotomy appropriate for internal tibial torsion?
A: Not before 8-10 years of age.
Related Pearl: Early surgery risks interfering with natural torsional remodeling and may lead to overcorrection.

Internal Tibial Torsion

Q: What degree of internal tibial torsion is considered abnormal?
A: More than 10° internal torsion is abnormal, considering normal 10° external thigh-foot angle.
Related Pearl: This equates to a 20° deviation from normal external rotation, causing intoeing and gait disturbance.

Osteochondritis Dissecans (OCD) Lesion

Q: What is the age threshold for prognosis and treatment approach in stable OCD lesions?
A: Age 12 years; under 12 has better prognosis, over 12 start conservative treatment but consider surgery if no improvement.
Related Pearl: Cartilage integrity may mask lesion severity; probing and drilling stimulate healing and revascularization.

IT Band Contracture

Q: What deformity pattern is seen with IT band contracture in polio patients?
A: Hip: flexion, abduction, external rotation; Knee: valgus, flexion, external rotation; hemipelvis tilts down on affected side; spine curves away (apex ipsilateral).
Related Pearl: Ipsilateral lumbar scoliosis apex helps localize the contracture side and guides surgical planning.

Equinus Contracture (Head Injury)

Q: How should severe equinus contractures in head-injured children be managed?
A: Use serial casting with well-padded casts; delay heel-cord lengthening until ?1 year post-injury.
Related Pearl: Spasticity often decreases over years; premature surgery may be unnecessary and complicate recovery.

Iliopsoas Tendon Transfer

Q: What are the prerequisites for iliopsoas tendon transfer?
A: Good rectus femoris, sartorius function, and active hip flexion.
Related Pearl: Adequate hip flexor strength is critical for transfer success and functional improvement.

Triplane Fracture

Q: Describe the fracture pattern in triplane ankle fractures.
A: Fracture of epiphysis in sagittal and coronal planes; metaphysis fracture in coronal plane; lateral rotation injury; posteromedial physis closure.
Related Pearl: Growth arrest is common but often clinically insignificant due to near skeletal maturity at injury.

Transmalleolar Axis

Q: How does the transmalleolar axis change with growth in children?
A: It tends to externally rotate, explaining natural correction of internal tibial torsion (intoeing).
Related Pearl: This physiological derotation reduces the need for surgical intervention in young children with intoeing.

Classic Clinical Notes

• A 5 year old with Blount’s and a 30 degree femoral-tibial angle should have an osteotomy – probably closing wedge. At this age, recurrence is high and the kid needs to be followed closely; may need repeat osteotomies down the road.

• In recurrent patellar dislocations, the starting point of treatment is lateral release, then a vastus medialis advancement (ie. proximal realignment).

• The Q angle is usually about 15 degrees. In males, the upper limit is about 17, in females it is about 20. Blumensatt’s line is seen at 30 degrees and the patella should go just above it. The Insall ratio compares the length of the patella and the length of the patellar tendon – the tendon should be no more than 1.2 times the length of the patella.

• Genu valgum is not uncommon in young kids, especially between the ages of 2-6 (that’s where it peaks). There is no particularly good conservative treatment for it – just let the natural history take its course, because the natural history is usually good. It can lead to patellofemoral problems. Consider surgery if the child reaches the age of 10 (give them up to this age to grow out of it) with 10 cm inter-malleolar distance or greater than 15-20 degrees of valgus.

• Be ready for the 9 year old that comes in with severe femoral anteversion and concomitant tibial external version (lateral tibial torsion) – should wait until the age of 10, but this will likely require double osteotomies (intertrochanteric and supramalleolar).

• Do not consider supramalleolar osteotomy for internal tibial torsion until at least the age of eight to 10.

• How much internal tibial torsion is too much? Probably 10 degrees. Remember that most people have a thigh foot angle that is externally rotated about 10 degrees, so this represents 20 degrees of abnormal internal torsion.

• In a 14 year old with a stable OCD lesion – the age threshold is about 12, so he is in the worse category. You’d start with conservative, but if he doesn’t improve, you may take the opportunity to get on with it and go after his lesion. Remember that you might have trouble seeing it if the cartilage is intact. Probe to see where it is soft and drill it to induce bone growth.

• Remember: age is key with OCD.

• If you have an IT band contracture (seen with polio kids) there will be a flexion, abduction, external rotation deformity of the hip and a valgus, flexion, and external rotation of the knee. The hemipelvis will tilt down on that side. The spine will then curve away from that side (ie. the apex will be on that side.) So a right IT band contracture will show a right lumbar scoliosis (apex to the right).

• For head injured kids, severe equinus contractures often develop which should be splinted or casted (with well padded casts) if possible. It often maximizes at 2-3 months post injury. These are often correctable with serial casting. The spasticity often decreases over the ensuing couple years, and so you should not do heel-cord lengthening on them until at least 1 year or more after injury.

• Pre-requisites for iliopsoas tendon transfer – good rectus femoris and sartorius and active flexion of hip.

• In triplane fractures, you see a fracture of the epiphysis in the sagittal plane and in the coronal plane, and you see a fracture of the metaphysis in the coronal plane. This is a lateral rotation injury related to the fact that the posteromedial part of the physis has already closed; a significant number of these have a growth arrest which is clinically not significant as they are near skeletal maturity.

• The transmalleolar axis tends to externally rotate in young children as they grow (this is why they grow out of their intoing for internal tibial torsion).

Last Updated on January 25, 2026 by Christian Veillette