Epidemiology
Rare
- 2:100 000
- 1/100 as common as DDH
- 1/3 bilateral
- F:M 2:1
Associations
45% DDH
30% CTEV
Larsen Syndrome
Down's Syndrome
Arthrogryposis
Aetiology
Unknown
Two Theories
1. Intra-uterine packaging defect
2. Quadriceps intrinsic contracture / fibrosis
Pathology
Knee hyperextended
- tibia dislocated anterior to the femur
Also
- quadriceps are tight
- absent cruciates
- patella hypoplastic or absent
- patella alta
- valgus deformity
- hamstrings act as extensors
Classification
Type 1
- can passively flex to 90°
- Subluxation / Hyperextension are minimal
Type 2
- can flex to 45°
- Moderate subluxation
Type 3
- -90 to 10o flexion
- complete dislocation
- no contact
DDx
Congenital Recurvatum of the Knee
- similar condition, but knee located
- hyperextension is correctable, but flexion is limited
- splint knee to increase flexion
- KFO to maintain flexion
- good prognosis
Management
Non operative
Type 1
Attempt closed reduction & Pavlik harness
Type 2 & 3
Gentle MUA & serial casting
Once 90o, Pavlik harness 3/12
If DDH as well
- reduce knee first
- usually splint from foot to hip till 45° flexion
- then Pavlik
Operative Management
Indication
Failure non-op treatment
Surgery often in syndrome e.g. arthrogryposis
Technique
Open reduction at 6/12 of age
- quadriceps engthening via anterior approach
- anterior capsulotomy / capsulectomy to reduce tibia onto femur
Ligamentous instability later very common