A 55-year-old male presents with significant knee recurvatum. Preoperative planning reveals a Mechanical Posterior Proximal Tibial Angle (mPPTA) of 88° and a normal Mechanical Posterior Distal Femoral Angle (mPDFA) of 82°. The surgeon, aiming for a '

Iatrogenic posterior knee subluxation

A 40-year-old patient with a history of distal femoral fracture malunion presents with 15 degrees of knee recurvatum. Radiographic analysis reveals a Mechanical Posterior Distal Femoral Angle (mPDFA) of 98° (normal 80-85°) and a normal Mechanical Pos

At the CORA within the distal femoral metaphysis, with simple angular correction

A patient with a severe knee deformity undergoes full-length weight-bearing lateral radiography. A plumb line dropped from the center of the femoral head passes significantly posterior to the center of the knee joint.

Knee hyperextension (recurvatum)

A 12-year-old patient with cerebral palsy presents with a 'recurvatum thrust' during the stance phase of gait, despite having normal Mechanical Posterior Distal Femoral Angle (mPDFA) and Mechanical Posterior Proximal Tibial Angle (mPPTA) measurements

Weak or paralyzed hamstrings leading to progressive attenuation of posterior static restraints

A 60-year-old patient with severe, long-standing knee flexion contracture (FFD) of 45 degrees presents for evaluation. A lateral radiograph shows the tibia appearing significantly translated posteriorly relative to the femur.

This is likely apparent subluxation due to the FFD; the primary focus should be on correcting the flexion contracture.

A surgeon is planning a proximal tibial flexion osteotomy for a patient with tibial recurvatum (Mechanical Posterior Proximal Tibial Angle (mPPTA) = 86°). The patient also has patella alta.

The osteotomy should be made proximal to the tibial tuberosity, which can simultaneously bring the patellar tendon down to a normal level.

During a distal femoral flexion osteotomy via a lateral sub-vastus approach for femoral recurvatum, the surgeon is performing an anterior opening wedge osteotomy.

Meticulously preserve the medial cortex as the bony hinge.

A patient with a distal femoral extension deformity (Mechanical Posterior Distal Femoral Angle (mPDFA) = 90°, Mechanical Posterior Proximal Tibial Angle (mPPTA) = 81°) undergoes a proximal tibial flexion osteotomy to correct their clinical hyperexten

Iatrogenic anterior knee subluxation

ABOS Part I & AAOS OITE Orthopedic Review: Sagittal Knee Deformity, Paley's Principles & Osteotomy | Part 21917

14 Apr 2026 1 min read 1 Views

Key Takeaway

Paley's Principles guide precise diagnosis and correction of sagittal knee deformities. They involve quantifying bony (femoral/tibial procurvatum/recurvatum via PDFA/PPTA) and soft tissue components. This dictates osteotomy planning at the CORA, ensuring corrections for recurvatum and fixed flexion deformity (FFD) are made at their anatomic source, preventing malalignment and optimizing outcomes.

ABOS Part I Comprehensive Review - Batch 34

This module contains 20 advanced orthopedic multiple-choice questions developed to mirror the American Board of Orthopaedic Surgery (ABOS) Part I and AAOS OITE examinations. Questions are derived directly from high-yield clinical teaching cases.

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ABOS Part I Comprehensive Review - Batch 34

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ABOS Part I & OITE Orthopaedic Review: Fibrous Dysplasia, Charcot, Rotator Cuff Tears & Shoulder Arthroplasty | Part 21549

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ABOS Part I Orthopaedic Deformity Correction, Limb Reconstruction & Gait Analysis Review | Part 21914

ABOS Part I & AAOS OITE Orthopedic Review: Sagittal Knee Deformity, Paley's Principles & Osteotomy | Part 21917

Key Takeaway

ABOS Part I Comprehensive Review - Batch 34

Module Results

You Might Also Like

ABOS Part I & OITE Orthopaedic Review: Fibrous Dysplasia, Charcot, Rotator Cuff Tears & Shoulder Arthroplasty | Part 21549

ABOS Part I Orthopaedic Exam: Sacral Fractures, Denis, VTE Prophylaxis, THA | Part 21569

Chapter Index

ABOS Part I Orthopaedic Deformity Correction, Limb Reconstruction & Gait Analysis Review | Part 21914

ABOS Part I & AAOS OITE Orthopedic Review: Sagittal Knee Deformity, Paley's Principles & Osteotomy | Part 21917

Key Takeaway

ABOS Part I Comprehensive Review - Batch 34

⚠️ Unanswered Questions

Module Results

You Might Also Like

ABOS Part I & OITE Orthopaedic Review: Fibrous Dysplasia, Charcot, Rotator Cuff Tears & Shoulder Arthroplasty | Part 21549

ABOS Part I Orthopaedic Exam: Sacral Fractures, Denis, VTE Prophylaxis, THA | Part 21569

Chapter Index