Congenital Dislocation of the Knee

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  • Congenital dislocation of the knee (CDK) is a rare condition affecting 1 per 100,000 live births.
  • Etiology is still unknown but several factors have been proposed, such as:
    1. Abnormal fetal positioning
    2. Quadriceps fibrosis/atrophy
    3. Patellar hypoplasia
    4. Contracture of iliotibial band
    5. Lack of formation or atrophy of suprapatellar pouch
    6. Lack or hypoplasia of cruciate ligaments.
  • One or both knees can be affected.
  • Bilateral CDK is almost always syndromic and is most commonly associated with arthrogryposis multiplex congenita, Larsen syndrome, inherited connective tissue disorder including Beal’s and Ehler-Danlos syndrome, and spinal dysrafism.

Moreover it has also being reported in association with other musculoskeletal abnormalities including DDH and clubfoot (70% and 50% of unilateral dislocations respectively), congenital vertical talus, and congenital dislocation of the elbow. 1,2

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Clinical photograph and plain x-ray of CDK.

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  • CDK can be diagnosed prenatally by ultrasound or at birth by clinical examination.
  • The knee is hyperextended and in true dislocations it cannot be flexed and the femoral condyles can be palpated in the popliteal fossa.
  • Radiographs show the position of the tibia relative to the femur and allow classification as:
    1. Grade I (severe genu recurvatum)
    2. Grade II (subluxation)
    3. Grade III (dislocation). 3
  • The main pathologic feature in CDK is a small quadriceps muscle, adherent to the distal femur. The quadriceps tendon is shortened and fibrotic and the patella is often dislocated laterally.
  • There is hypoplasia of the suprapatellar pouch and the hamstrings are often deficient and/or subluxated anteriorly. 4

Treatment should be started as soon as possible.

Conservative treatment

Consists of gentle manipulation and serial casting aiming to achieve at least 90 degrees of flexion. Removable splints can be used to maintain the position obtained. Conservative treatment is often successful in idiopathic CDK but results are less predictable in syndromic CKD. 1-4

Surgical treatment

Operative treatment is indicated if manipulations and serial casting fail. This can be done between 6 months to 1 year of age.

Classically, surgical treatment for CDK was a distal V-Y Quadricepsplasty (Thompson’s procedure) 5 usually complicated by a severe extension lag.

Proximal sequential quadricepsplasty in association with release of the intra-articular adhesions and mobilization of the suprapatellar pouch (Judet’s technique) 6 showed better clinical results and became more popular.

In recent years, femoral shortening osteotomy has been done to minimize the extensive quadriceps release, while anterior cruciate ligament (ACL) reconstruction has been associated to address the coexistent ligaments deficiency. 7,8

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References

  • 1. Johnson E, Audell R, Oppenheim WL. Congenital dislocation of the knee. J Pediatr Orthop. 1987;7:194–200.
  • 2. Jacobsen K, Vopalecky F: Congenital dislocation of the knee. Acta Orthop Scand 1985;56:1-7.
  • 3. Curtis BH, Fisher RL: Congenital hyperextension with anterior subluxation of the knee: Surgical treatment and long-term observations. J Bone Joint Surg Am 1969;51:255-269.
  • 4. Ooishi T, Sugioka Y, Matsumoto S, et al. Congenital dislocation of the knee. Its pathologic features and treatment. Clin Orthop Relat Res. 1993;216:187–192.
  • 5. Thompson T.C.: Quadricepsplasty to improve knee function. J Bone Joint Surg Am 1944; 26:366-378
  • 6. Judet R, Judet J, lagrange J: Une technique de liberation de l’appareiul extenseur dans les raideurs du genou. Med. Acad. Chir. 1956; 82:944-947
  • 7. Johnston CE 2nd. Simultaneous open reduction of ipsilateral congenital dislocation of the hip and knee assisted by femoral diaphyseal shortening. J Pediatr Orthop. 2011 Oct-Nov;31(7):732-40.
  • 8. Klingele KE1, Stephens S. Management of ACL elongation in the surgical treatment of congenital knee dislocation. Orthopedics. 2012 Jul 1;35(7):e1094-8.