Hyperextension Deformity | Neonatal Presentation | Quadriceps Contracture
TAREK GRADING (CLINICAL)
Critical Must-Knows
- CDK = knee hyperextension or anterior dislocation present at birth
- Tibia displaced anterior to femur; quadriceps and anterior capsule contracted
- Strong association with DDH (screen hips), clubfoot, arthrogryposis, Larsen syndrome
- Grade I and II usually respond to serial casting within 6-8 weeks
- Grade III or resistant cases require quadricepsplasty (V-Y lengthening or Curtis-Fisher)
Clinical Pearls
- "Always screen hips in CDK: DDH coexists in up to 40-100 percent of cases
- "Hyperextension at birth is CDK until proven otherwise
- "Serial casting reduces the knee in stages: hyperextension to neutral to flexion
- "Failed closed treatment by 3 months strongly indicates surgical intervention
Critical Exam Points for Congenital Knee Dislocation
Definition
CDK = anterior displacement of the tibia relative to the femur at birth. Ranges from simple genu recurvatum (hyperextension) through subluxation to complete dislocation. The quadriceps mechanism and anterior joint capsule are contracted and the knee cannot be flexed passively beyond a right angle in severe cases.
Associations
CDK is rarely isolated. DDH coexists in 40-100 percent, clubfoot in 30-50 percent. Consider underlying arthrogryposis multiplex congenita or Larsen syndrome when multiple joint contractures or dislocations are present. Always perform a full musculoskeletal examination of the newborn.
Treatment Principle
Gradual reduction by serial casting. Casts are changed weekly, progressively increasing knee flexion. The goal is to achieve at least 90 degrees of knee flexion and a stable reduction. Grade I and II cases usually reduce within 6-8 weeks of casting.
Surgical Threshold
Failure of closed treatment by 3 months of age indicates need for quadricepsplasty. The Curtis-Fisher procedure (V-Y quadriceps lengthening with anterior capsular release) is the standard operation. Delaying surgery risks growth disturbance and persistent deformity.
Quick Decision Guide
| Presentation | Tarek Grade | Treatment | Key Pearl |
|---|---|---|---|
| Knee hyperextends but reduces with flexion | Grade I (genu recurvatum) | Passive stretching + serial casting 4-6 weeks | Best prognosis, nearly always successful |
| Anterior subluxation, reducible under anaesthesia | Grade II (subluxation) | Serial casting with progressive flexion | Majority resolve, screen for DDH |
| Fixed anterior dislocation, irreducible | Grade III (complete dislocation) | Serial casting trial, then quadricepsplasty | High surgical rate, check for Larsen syndrome |
KNEELCongenital Knee Dislocation Associations
| K | Knee (CDK itself) The index condition: hyperextension or anterior dislocation at birth |
| N | Neonatal hip (DDH) Screen hips with ultrasound; DDH coexists in 40-100 percent |
| E | Equinovarus (clubfoot) Foot deformity present in 30-50 percent of CDK cases |
| E | Extra joints (arthrogryposis) Multiple contractures suggest arthrogryposis multiplex congenita |
| L | Larsen syndrome Multiple joint dislocations (knees, hips, elbows) with characteristic facies |
| K | Knee (CDK itself) The index condition: hyperextension or anterior dislocation at birth | E | Extra joints (arthrogryposis) Multiple contractures suggest arthrogryposis multiplex congenita |
| N | Neonatal hip (DDH) Screen hips with ultrasound; DDH coexists in 40-100 percent | L | Larsen syndrome Multiple joint dislocations (knees, hips, elbows) with characteristic facies |
| E | Equinovarus (clubfoot) Foot deformity present in 30-50 percent of CDK cases |
Hook:KNEEL at birth and check every joint!
CASTSCDK Treatment Ladder
| C | Commence early Begin serial casting within the first few days of life |
| A | Advance flexion weekly Each cast increases knee flexion by 10-15 degrees |
| S | Screen hips and feet Always investigate for DDH and clubfoot simultaneously |
| T | Three-month limit If no reduction by 3 months, plan quadricepsplasty |
| S | Surgery: Curtis-Fisher V-Y quadriceps lengthening + anterior capsular release is gold standard |
| C | Commence early Begin serial casting within the first few days of life | T | Three-month limit If no reduction by 3 months, plan quadricepsplasty |
| A | Advance flexion weekly Each cast increases knee flexion by 10-15 degrees | S | Surgery: Curtis-Fisher V-Y quadriceps lengthening + anterior capsular release is gold standard |
| S | Screen hips and feet Always investigate for DDH and clubfoot simultaneously |
Hook:CASTS early, measure progress weekly, operate by 3 months if needed!
RELEASEQuadricepsplasty Key Steps
| R | Release anterior capsule Divide the contracted anterior joint capsule from medial and lateral |
| E | Evaluate tibiofemoral reduction Confirm congruent reduction under direct vision |
| L | Lengthen quadriceps (V-Y) Curtis-Fisher V-Y plasty of the quadriceps tendon |
| E | Ensure neurovascular status Check peroneal nerve and popliteal vessels after flexion |
| A | Apply long-leg cast at 90 degrees Splint in at least 90 degrees of flexion post-operatively |
| S | Serial casting continues post-op Gradual wean and range-of-motion programme |
| E | Early DDH treatment Address concomitant DDH with Pavlik harness or spica |
| R | Release anterior capsule Divide the contracted anterior joint capsule from medial and lateral | E | Ensure neurovascular status Check peroneal nerve and popliteal vessels after flexion | E | Early DDH treatment Address concomitant DDH with Pavlik harness or spica |
| E | Evaluate tibiofemoral reduction Confirm congruent reduction under direct vision | A | Apply long-leg cast at 90 degrees Splint in at least 90 degrees of flexion post-operatively | ||
| L | Lengthen quadriceps (V-Y) Curtis-Fisher V-Y plasty of the quadriceps tendon | S | Serial casting continues post-op Gradual wean and range-of-motion programme |
Hook:RELEASE the contracted quadriceps and anterior capsule to achieve reduction!
Overview and Epidemiology
Why This Matters
Congenital dislocation of the knee (CDK) is a rare but important neonatal condition where the knee presents in hyperextension or frank anterior dislocation at birth. It sits on a spectrum from simple genu recurvatum to irreducible anterior dislocation. Early recognition is critical because outcomes are excellent with prompt serial casting, but delayed or inadequate treatment leads to progressive deformity, growth disturbance, and the need for complex surgery. The high association with DDH means every CDK baby must have hip screening.
Incidence and Demographics
- Incidence: approximately 1 per 100,000 live births
- Female-to-male ratio: roughly 2:1 to 3:1 female predominance
- Laterality: bilateral in roughly 40-60 percent of cases
- Family history: most cases sporadic; familial forms reported
Clinical Impact
- Ambulation: untreated CDK causes severe gait disturbance
- Growth: chronic anterior displacement can distort distal femoral physis
- Function: knee instability limits standing, walking, and sitting
- Psychosocial: cosmetic deformity and functional limitation in childhood
Pathophysiology
Aetiology and Pathomechanics of CDK
The exact aetiology of CDK remains debated, but two main theories prevail. The mechanical theory attributes CDK to intrauterine positioning (breech presentation with feet trapped under the chin or against the uterine wall), leading to sustained knee hyperextension. The muscular theory emphasises primary quadriceps fibrosis and contracture as the driving force, analogous to the contracture seen in arthrogryposis. In severe cases (Grade III), the quadriceps tendon, patellar ligament, and anterior joint capsule are all contracted and shortened. The tibia is displaced anteriorly and laterally relative to the femur, the suprapatellar pouch is obliterated, and the hamstring muscles are attenuated and displaced anteriorly. The cruciate ligaments may be absent, attenuated, or abnormally positioned.
Pathoanatomy by Grade
| Structure | Grade I (Recurvatum) | Grade II (Subluxation) | Grade III (Dislocation) |
|---|---|---|---|
| Quadriceps | Mild contracture | Moderate contracture | Severe fibrosis and shortening |
| Anterior capsule | Lax or minimally tight | Contracted | Severely contracted, suprapatellar pouch obliterated |
| Hamstrings | Normal position | Mild anterior displacement | Displaced anteriorly, become knee extensors |
| Cruciate ligaments | Usually present | May be attenuated | Often absent or severely abnormal |
| Tibiofemoral joint | Congruent, hyperextends | Subluxed anteriorly | Completely dislocated anteriorly |
Mechanical Theory
Breech positioning: foot locked against chin or uterine wall
Oligohydramnios: restricts movement, maintains hyperextension
First-born: tighter uterus, less room for movement
Evidence: association with breech presentation and oligohydramnios supports mechanical compression
Muscular Theory
Quadriceps fibrosis: primary muscular abnormality similar to arthrogryposis
Absence of cruciates: suggests developmental arrest rather than pure positioning
Genetic cases: familial CDK and syndromic forms (Larsen) support inherent tissue abnormality
Spectrum: CDK may represent a continuum from positional deformity to true congenital absence of joint formation
Classification and Types
Tarek Classification of CDK (Most Commonly Used)
| Grade | Clinical Finding | Pathoanatomy | Reduction | Treatment |
|---|---|---|---|---|
| Grade I | Genu recurvatum (hyperextension) | Mild quadriceps tightness, joint congruent | Passively correctable to flexion | Serial casting, excellent prognosis |
| Grade II | Anterior subluxation of tibia | Moderate quadriceps contracture, capsule tight | Reducible under gentle manipulation | Serial casting, majority resolve |
| Grade III | Complete anterior dislocation | Severe fibrosis, capsule contracted, cruciates absent | Irreducible or requires significant force | Casting trial, most need quadricepsplasty |
The Tarek grading guides both prognosis and treatment selection. Grade I is essentially a severe hyperextension deformity without displacement, Grade II involves anterior subluxation that reduces, and Grade III represents a fixed dislocation.
Clinical Assessment
History
- Prenatal: breech presentation, oligohydramnios, prenatal ultrasound findings
- Birth: hyperextended knee noted at delivery
- Family: consanguinity, familial joint disorders
- Other joints: foot deformity, hip click or limited abduction
Examination
- Inspect: knee in hyperextension or anterior dislocation; skin folds may be abnormal
- Palpate: patella position (may be displaced or poorly palpable), tibiofemoral relationship
- Range of motion: assess passive flexion; Grade III cannot flex beyond a right angle
- Hips: Ortolani and Barlow tests, limited abduction
- Feet: check for clubfoot or other foot deformities
Essential Examination Steps in CDK
Every newborn with CDK must have:
- Both knees examined (40-60 percent bilateral)
- Both hips screened by clinical examination (Ortolani, Barlow, abduction) AND hip ultrasound at 6 weeks
- Both feet examined for clubfoot
- Full musculoskeletal survey checking elbows, shoulders, and spine for other contractures or dislocations
- Neurological examination to exclude myelodysplasia
- Dysmorphology assessment for Larsen syndrome features (prominent forehead, hypertelorism, depressed nasal bridge)
Failing to screen for DDH in a baby with CDK is a significant clinical error.
Differential Diagnosis of Hyperextended Knee at Birth
| Condition | Key Feature | Discriminating Finding | Management |
|---|---|---|---|
| Congenital dislocation of the knee | Hyperextension or anterior dislocation at birth | Anterior tibial displacement, tight quadriceps | Serial casting, possible quadricepsplasty |
| Benign hyperextension (positional) | Hyperextends but flexes fully and easily | No fixed deformity, reduces with gentle flexion | Observation, usually resolves spontaneously |
| Congenital quadriceps contracture (isolated) | Limited flexion without frank dislocation | Quadriceps tight, joint not subluxed | Stretching programme, rarely surgery |
| Arthrogryposis (knee involvement) | Stiff knee with multiple other joint contractures | Multiple rigid joints, absent skin creases | Multidisciplinary, early casting, often surgical |
| Larsen syndrome | Multiple large joint dislocations | Bilateral knee dislocations, hip dislocations, characteristic facies | Genetic workup, staged surgical reduction |
Distinguishing Positional Hyperextension from True CDK
A positional hyperextended knee is soft and passively correctable to full flexion without resistance. The tibiofemoral joint is congruent on radiographs. True CDK has a firm endpoint to passive flexion, the tibia is anteriorly displaced, and radiographs show anterior subluxation or dislocation. If you can flex the knee to 90 degrees easily with no firm resistance, it is likely positional and will resolve without casting.
Investigations
Imaging Protocol
Views: AP and lateral of both knees
Look for: Anterior displacement of tibia relative to femur on lateral view, patella position, physeal status
Grade I: May appear near-normal with hyperextension only
Grade III: Obvious anterior tibial displacement, tibia anterior to femoral condyles
Indication: Mandatory in all CDK cases regardless of clinical hip examination
Method: Graf technique or dynamic ultrasound
Findings: DDH may be missed on clinical exam when knees are stiff
Action: Positive findings require immediate DDH treatment (Pavlik harness or surgical)
Indication: Grade III or syndromic cases before quadricepsplasty
Findings: Cruciate ligament status, meniscal position, cartilage integrity
Surgical planning: Identifies absent or abnormal structures that affect surgical approach
Indication: Bilateral CDK, multiple joint dislocations, dysmorphic features
Look for: Spinal anomalies, other joint dislocations, skeletal dysplasia features
Genetics: FLNB gene testing for Larsen syndrome; chromosome analysis if indicated
Imaging Pearl
The diagnosis of CDK is primarily clinical. Plain radiographs confirm the degree of tibial displacement and guide grading. The most important investigation is hip ultrasound at 6 weeks, because DDH coexists so frequently and has its own treatment window. Do not delay casting while waiting for advanced imaging.
Management Algorithm
Serial Casting Protocol (First-Line for All Grades)
Goal: Achieve congruent reduction and at least 90 degrees of knee flexion through gradual, weekly casting
Serial Casting Protocol
Position: Knee in maximum obtainable flexion (even if still hyperextended initially)
Technique: Long-leg plaster cast, well-padded, moulded to hold tibia posteriorly
Goal: Correct hyperextension toward neutral
Caution: Never force flexion; risk of physeal injury or neurovascular compromise
Weekly cast changes: Increase flexion by 10-15 degrees per week
Moulding: Posterior force on tibia to maintain reduction as flexion increases
Monitor: Skin integrity, neurovascular status, hip position
Grade I response: Typically achieves neutral to 30 degrees flexion by week 2-3
Target: At least 90 degrees of knee flexion with stable reduction
Grade I and II: Usually reduced and stable by 6-8 weeks
Grade III: May still have anterior tibial displacement; if no progress, plan surgery
Transition: From casting to bracing once stable
Bracing: Night-time knee flexion splint for additional 4-6 weeks
Range of motion: Gentle passive and active exercises
Monitor: Relapse into hyperextension, hip stability, gait development
DDH treatment: Concurrent Pavlik harness or spica as indicated
Casting Pearl
The key principle is gradual, weekly progression of flexion. Never force the knee into flexion in a single cast change, as this risks physeal injury (distal femoral or proximal tibial growth plate), peroneal nerve palsy, or femoral fracture. If reduction is not progressing after 6-8 weeks of proper serial casting, surgical intervention is indicated rather than continuing futile casting.
Complications
| Complication | Incidence | Risk Factors | Management |
|---|---|---|---|
| Residual hyperextension deformity | 10-20 percent after casting alone | Grade III, syndromic, delayed treatment | Night splinting, extension osteotomy if severe in older child |
| Peroneal nerve palsy | Rare but reported with forced flexion | Aggressive casting, intraoperative hyperflexion | Immediate release of flexion position, nerve exploration if no recovery |
| Physeal injury (distal femur or proximal tibia) | Rare with proper technique | Forced manipulation during casting or surgery | Monitor growth with serial radiographs; reconstructive osteotomy if deformity develops |
| Knee instability (recurrent subluxation) | 15-25 percent in Grade III | Absent cruciate ligaments, inadequate capsular release | Cruciate reconstruction in older child, brace management |
| Stiffness (limited flexion) | Common after quadricepsplasty | Scarring, arthrogryposis | Physiotherapy, gentle manipulation under anaesthesia |
| Missed DDH | Significant if hips not screened | Failure to perform hip ultrasound | Late DDH treatment is more complex; always screen hips early |
Prevention of Complications
The most important preventable complication is missed DDH. Every child with CDK must have hip screening by clinical examination at birth and ultrasound at 6 weeks. The second key preventable problem is physeal injury from forced manipulation. Cast changes should progress gradually; never force the knee beyond what it will comfortably accept. Finally, peroneal nerve palsy is prevented by avoiding excessive flexion in a single cast and by monitoring neurovascular status after every cast change.
Outcomes and Prognosis
Outcomes by Grade and Treatment
| Grade / Treatment | Functional Outcome | Residual Deformity | Long-term Function |
|---|---|---|---|
| Grade I with serial casting | Excellent; near-normal ROM | Minimal or none | Normal gait and activities |
| Grade II with serial casting | Good to excellent | Mild residual hyperextension possible | Functional gait, may have mild cosmetic concern |
| Grade III with quadricepsplasty | Good functional result | Variable; residual laxity or stiffness common | Ambulatory, may have limitations in high-demand activities |
| Syndromic CDK (arthrogryposis) | Guarded | Residual stiffness and deformity common | Ambulation achievable but with limitations |
| Larsen syndrome | Variable | Multiple joint issues persist | Requires lifelong multidisciplinary care |
Prognostic Factors
Best prognosis: Grade I or II, isolated CDK (no syndrome), treatment started within first week of life, compliant serial casting
Poor prognosis: Grade III, bilateral involvement, underlying arthrogryposis or Larsen syndrome, delayed treatment initiation beyond 3 months
Key threshold: 3 months of age is the practical cutoff for casting. Beyond this, surgical success rates decline and residual deformity becomes more likely.
Evidence Base and Key Trials
Quadricepsplasty for congenital dislocation of the knee and congenital quadriceps contracture
- Described a structured quadricepsplasty technique for resistant CDK and congenital quadriceps contracture
- V-Y quadriceps lengthening with anterior capsular release achieved reduction in the majority of cases
- Grade I and II cases responded to serial casting; Grade III cases frequently required quadricepsplasty
- Emphasised the importance of anterior capsular release in addition to quadriceps lengthening for severe knees
Congenital hyperextension with anterior subluxation of the knee: surgical treatment and long-term observations
- Described the V-Y quadriceps lengthening with anterior capsular release for resistant CDK
- Reported successful reduction in the majority of cases unresponsive to casting
- Emphasised the importance of anterior capsular release in addition to quadriceps lengthening
- Recommended casting for at least 6 weeks before considering surgical intervention
A minimally invasive treatment protocol for the congenital dislocation of the knee
- Described a minimally invasive treatment protocol using serial casting and percutaneous quadriceps tenotomy
- Grade I and II knees achieved reduction with casting alone within a mean of 4-6 weeks
- Grade III knees often required percutaneous quadriceps tenotomy in addition to casting
- Concluded that early initiation of treatment was the strongest predictor of successful non-operative management
Functional results after surgical treatment for congenital knee dislocation
- Long-term functional follow-up of patients treated surgically for CDK
- Patients treated non-operatively had better outcomes than those requiring quadricepsplasty
- Residual quadriceps weakness was common after surgical lengthening
- Knee alignment and function were generally acceptable but rarely normalised
Long-term outcomes of surgically treated congenital dislocation of the knee
- Long-term outcomes of surgically treated CDK with mean follow-up exceeding 10 years
- Reduction was achieved in most cases, but functional ROM was limited compared to unaffected knees
- Multiple procedures were frequently required in syndromic cases including arthrogryposis
- Recommended staged surgical approach addressing knees before hips in bilateral cases
Exam Viva Scenarios
Use these scenarios to practise clinical reasoning and management decisions
Scenario 1: Neonatal Knee Hyperextension
"A newborn girl is noted at delivery to have a hyperextended left knee. The knee rests at 30 degrees of hyperextension. It can be flexed passively to 60 degrees but with firm resistance. The right knee is normal. The baby was born in breech position. What is your diagnosis, classification, and management plan?"
Scenario 2: Resistant Grade III Dislocation
"A 4-month-old infant with bilateral congenital knee dislocations has undergone 12 weeks of serial casting without achieving reduction. The knees remain in anterior dislocation with fixed hyperextension. The child also has bilateral hip dislocations. No dysmorphic features are noted. What is your next step?"
MCQ Practice Points
Classification Question
Q: What is the Tarek classification of congenital knee dislocation? A: Grade I = genu recurvatum (hyperextension without displacement, reducible). Grade II = anterior subluxation of tibia on femur (reducible with manipulation). Grade III = complete anterior dislocation (irreducible or requires significant force). Grade correlates with treatment: Grades I and II usually respond to casting; Grade III often requires quadricepsplasty.
Association Question
Q: What is the most common association with congenital dislocation of the knee? A: Developmental dysplasia of the hip (DDH), reported in 40-100 percent of CDK cases. Every newborn with CDK must have clinical hip examination (Ortolani, Barlow) and hip ultrasound at 6 weeks. Other common associations include clubfoot (30-50 percent), arthrogryposis, and Larsen syndrome.
Treatment Question
Q: What is the first-line treatment for congenital dislocation of the knee? A: Serial long-leg casting, beginning immediately after birth. Casts are changed weekly with progressive increase in knee flexion of 10-15 degrees per week. The goal is congruent reduction with at least 90 degrees of flexion within 6-8 weeks. If casting fails by 3 months, surgical quadricepsplasty (Curtis-Fisher procedure) is indicated.
Surgical Question
Q: Describe the Curtis-Fisher quadricepsplasty for resistant CDK. A: V-Y lengthening of the quadriceps tendon combined with anterior capsular release. Through an anterior longitudinal incision, the contracted anterior capsule is released medially and laterally, the quadriceps tendon is divided in a V pattern and repaired in a lengthened Y configuration, and tibiofemoral reduction is confirmed. Post-operative casting at 60-90 degrees flexion for 4-6 weeks.
Syndrome Question
Q: What syndrome should you suspect in a newborn with bilateral knee dislocations, bilateral hip dislocations, and characteristic facies? A: Larsen syndrome, an autosomal dominant or recessive condition caused by FLNB gene mutations. Features include multiple large joint dislocations, prominent forehead, hypertelorism, depressed nasal bridge, and spinal anomalies (scoliosis, cervical kyphosis). Management requires staged surgical treatment and genetic counselling.
Guidelines, Registries & Global Practice
Global Epidemiology
- CDK incidence approximately 1 per 100,000 live births worldwide
- Female predominance (2:1 to 3:1) consistently reported across populations
- Breech association reported globally but may vary with local breech delivery rates
- Syndromic forms (arthrogryposis, Larsen) appear to have similar prevalence across ethnic groups
Practice Variation by Resource Setting
- High-resource: neonatal identification, immediate serial casting with paediatric orthopaedic follow-up, MRI pre-operatively
- Limited-resource: diagnosis may be delayed; plaster casting is low-cost and effective; surgery in specialist paediatric centres
- Universal principle: serial casting is the first-line treatment globally, regardless of resources
- Key message: the cost of treatment is in the expertise and follow-up, not the materials
Society and Reference Guidance (Side by Side)
| Source | Diagnosis | Conservative Treatment | Surgical Approach |
|---|---|---|---|
| POSNA / Paediatric Orthopaedic Societies | Clinical examination + lateral radiograph; classify by Tarek | Serial casting from birth, weekly changes, 6-8 week target | Curtis-Fisher quadricepsplasty at 3-6 months if casting fails |
| BSCOS / EPOS (European) | Same clinical-radiographic approach; mandatory hip screening | Same serial casting principles; some advocate earlier surgical referral for Grade III | V-Y quadricepsplasty; some centres use percutaneous techniques for selected cases |
| AAOS / POSAN (US) | Clinical grading + AP/lateral knee radiographs + hip ultrasound | Immediate serial casting; 3-month threshold for surgical decision | Curtis-Fisher or modifications; cruciate reconstruction considered in older children |
Evidence Note
There is no dedicated registry for congenital knee dislocation. The evidence base consists entirely of retrospective case series and expert opinion. No randomised controlled trials exist comparing casting protocols or surgical techniques. Management is therefore guided by clinical grading (Tarek), institutional experience, and the consistent principle that early, gradual serial casting gives the best outcomes for Grades I and II.
Essential Documentation in CDK
Record in every newborn with CDK:
- Tarek grade (I, II, or III) with clinical description
- Serial casting start date and weekly flexion progression
- Hip examination findings and hip ultrasound arranged
- Foot examination findings
- Full musculoskeletal survey for other contractures or dislocations
- Genetic or syndromic referral if bilateral or Grade III
- Parent counselling: treatment plan, timeline, and prognosis
Missed DDH in a child with CDK is a recurring and preventable error. Always document hip screening in the CDK chart.
CONGENITAL DISLOCATION OF THE KNEE
Clinical summary
Key Facts
- •CDK = hyperextension or anterior dislocation of the knee present at birth
- •Incidence approximately 1 per 100,000 live births; female predominance 2-3:1
- •Tarek grading: Grade I (recurvatum), Grade II (subluxation), Grade III (complete dislocation)
- •Quadriceps fibrosis and anterior capsule contracture are the primary pathoanatomy
Associations (Must Screen)
- •DDH: 40-100 percent association; clinical exam + hip ultrasound mandatory
- •Clubfoot: 30-50 percent; examine both feet at birth
- •Arthrogryposis: multiple joint contractures suggest underlying myopathic or neuropathic cause
- •Larsen syndrome: multiple joint dislocations with flat facies; FLNB gene
Treatment Ladder
- •First-line: serial casting from birth, weekly changes, progressive flexion 10-15 degrees per week
- •Target: congruent reduction with at least 90 degrees flexion within 6-8 weeks
- •If casting fails by 3 months: Curtis-Fisher quadricepsplasty (V-Y lengthening + anterior capsular release)
- •Syndromic CDK: higher surgical rate; staged procedures; realistic expectations
Surgical Details
- •Curtis-Fisher: anterior approach, V-Y quadriceps lengthening, anterior capsule release
- •Intraoperatively assess cruciate ligaments (often absent in Grade III)
- •Post-op: long-leg cast at 60-90 degrees flexion for 4-6 weeks
- •Address DDH after knee stability is achieved (staged approach)
Complications
- •Residual hyperextension: night splinting, osteotomy if severe in older child
- •Peroneal nerve palsy: avoid forced flexion; immediate release if occurs
- •Physeal injury: never force manipulation; monitor growth serially
- •Missed DDH: the most preventable error; always screen hips in CDK