Epidemiology
Rare - 1 in 100,000
1/3 bilateral
Etiology
Idiopathic - ? insufficient in utero space
Syndromes - Larsen syndrome, Arthrogryposis
Hyperlaxity - Marfan's, Ehler-Danlos
Other - ACL deficiency / quadriceps contracture
Clinical
Hyper-extended knee - unilateral / bilateral
Image from: Cirakli et al Jt Disease Relat Surg 2021
Associations - DDH / CTEV
Image from:Mota et al Cureus 2022
Pathology
Tight quadriceps
Hypoplastic / absent patella
Absent cruciates
Tarek grading
Based upon clinical assessment and xray
| Type I | Type II | Type II |
|---|---|---|
| Hyper-extension | Subluxation | Dislocation |
| Reducible | Reducible but unstable | Irreducible |
Non operative management
Options
Type I - Pavlik harness
Type II - serial casting
Images from: Afonso et al Cureus 2025
Results
Yousseff et al J Pediatr Orthop 2017
- 13 idiopathic congenital knee dislocations
- 9 bilateral and 4 unilateral for total of 22 knees
- serial casting at mean of 5 weeks successful in 6/22 knees (27%)
Operative Management
Indication
Failure non-op treatment
Syndrome such as arthrogryposis
Technique
Options
Percutaneous quadriceps tenotomy
Open quadricepsplasty - quadriceps release / Z lengthen
Femoral diaphyseal shortening
Results
Percutaneous quadriceps tenotomy
Patwardhan et al Int Orthop 2015
- 20 cases of flexible knee dislocation
- percutaneous tenotomy at mean 2 weeks
- mean pre-operative hyperextension was 50°
- all patients were able to achieve >90° flexion intra-operatively
- mean knee flexion at walking age was 135° (range, 130-140°)
- good results in nine patients and fair result in three patients
- no extensor lag with intact quadriceps on follow up ultrasound
Open quadricepsplasty
Honcharuk et al J Pediatr Orthop 2024
- 12 cases of congenital knee dislocation treated surgically with long term follow up
- 3 idiopathic, 5 Larsen syndrome, 4 arthrogryposis
- some treated with quadricepsplasty, some femoral shortening
- all had ongoing abnormal gait and knee examination
- better outcomes with idiopathic
- better outcomes with femoral shortening
Yousseff et al J Pediatr Orthop 2017
- 16 idiopathic congenital knee dislocations with failed serial casting
- treated with limited open quadriceps release at mean 10 weeks
- mean ROM 110 degrees
- mean FFD 9 degrees)
- 6 excellent outcomes, 10 good outcomes