Congenital Dislocation of the Knee
A congenital dislocation (CDK) of the knee is a relatively rare condition with an unknown incidence. In a study performed in Scandinavia from 1963 to 1980, 13 patients were discovered with 19 dislocated knees. It may occur as an isolated deformity or may be associated with other musculoskeletal anomalies… such as developmental hip dysplasia, clubfeet deformity or be part of a syndrome such as arthrogryposis multiples congenita or Larsen syndrome or even can happen in paralytic conditions such as myelomeningocele, or in amniotic band syndrome, Ehlers Danlos syndrome, Down Syndrome, Beals syndrome and Larsen syndrome.
Various other causes were discovered in the study like muscular imbalance in 9 patients, spinal abnormality in four cases with obvious neuromuscular imbalance. It was estimated that hip dislocation (DDH) was found to be at a 1 % incidence. A gentle manipulation was performed in order to avoid any hip problems necessitating surgical treatment especially a slipped capital epiphysis over a period of three months.
Others can define it like a subluxation of the tibia on the femur with an anterior displacement of the tibia present at birth manifesting a hyperextension of the knee with shortening of the extensor mechanism (Quadriceps muscle) with or without valgus malposition and often the cruciate ligaments can be deficient forcing the knee cap to displace laterally. In 1822, Chatelain was the first one who described the entity in a frequency of 1.5% per 100,000 births. Others like Drennan (1993) and Jacobsen (1985) described a 1% incidence in their study comparing it to the same incidence encountered in Developmental Hip Dysplasia (DDH).
Some found a strong familial tendency but the exact cause of this sporadic malformation is not well known. Perhaps a malposition in the womb, or a fibrosis of the extensor mechanism of the knee (Quadriceps) can explain it with the lack of cruciate ligaments. A recent case seen at the Nursery is presented in our AMHE Newsletter and may it reminds all our residents the way to approach such baby hours after the delivery.
A 6 and half pounds baby girl, born from a 16-year-old mother, G1-P1, mildly obese after an uncomplicated pregnancy, is seen in consultation on the nursery floor. She jus delivered six hours ago a healthy baby, presented in a Vertex (cephalic) position. We are consulted around 6 hours after the delivery.
A deformity of the left knee is well apparent at birth and we are responding to a request of her pediatrician for an orthopedic consult at the nursery. I have already requested radiologic studies of the left lower extremities prior to arrival. I would have been able to request an ultrsound and the pathology would have been as well as apparent. The patella is not ossified yet and surely not visible, but it can be easily palpated anteriorly or laterally to these deformed knee when present. In this case, if a recurvatum is is pronounced and no contact is found between the tibia and the femur, the presence or the absence of the cruciate ligaments can be proven by examination or rarely an MRI study can be ordered if needed..
For the orthopedic consultant, an experienced observator will be the best specialist to perform a complete orthopedic examination of the infant. Attention should be given to all extremities and any other anomalies need to be looked for. The hip stability for the search of developmental hip dysplasia or any deformation of the feet can explain the reason why such pathology was discovered in the newborn. The orthopedic treatment of a congenital knee dislocatio, should take place as soon as possible with the stretching of the muscle around the knee joint.
Some babies may require sedation or even general anesthesia while perform the stretching althrough in most of the cases, we can manipulate the knee at the nursery and cast or splint it. Once the knee positionning becomes acceptable, casting in flexion can easily be performed. Rarely a surgical treatment on the quadriceps muscles and the extensor mechanism for a lengthning procedure may be necessary. Soft tissue release may be needed while the range of motion will depend also on the presence or the absence of cruciate ligaments. The laxity of the capsule will also play a role in the manipulation of the knee in the desired position. Other soft tissues may require release while a reconstruction of the cruciate ligaments is performed. Other procedures can focus on a shortning the femur.
The clinical findings may varyto a hyperextension contractures with transverse anterior skin folds to to the shortening of the extensor mechanism. Sometimes the quadriceps becomes fibrotic with a thight anterior capsule of the knee and sometimes a fibrotic quadriceps forcing the hamstring to displace anteriorly rendering the cruciate non-functional. The knee hyperextension can be so extreme that the feet reach the face or the head of the baby while he is laying supine on the examining bed or table.
Congenitsl knee dislocation is often seen following a breech positionning (30%), with clubfoot deformity (47%) or hip dislocation (50%) suggesting a mechanical cause such as decrease in the intra-uterine space or fetal mal-positionning as described in many papers published by Niebauer (1960), Curtis (1969), Johnson (1987), Ko (1999). In absence of any syndrome, the initial range of motion and the time of the consultation forbeginning the treatment represent the best prognostic indicators.
Pre-natal ultrsound has been used to diagnose congenital knee dislocation (Monteagudo 2006). Rarely cases have been diagnosed by simple abdominal radiographhs (Lage1986 and Elchalal 1993). One has to remember that the diagnosis of such pathology is is base on clinical examinationand the radiographic studies are used to confirm the diagnosis. The radiographs will confirm the contact between the tibia and the femur.
Congenital Knee Dislocation (CKD) has common classifications described by Neibauer (1960) and Curtis (1969) in which a grade 1 or type A representing a simple hyperextension of the knee (Recurvatum), a grade 2 or type B, where the tibia is subluxated anteriorly to the femur but still reducible once flexion is applied to the knee and finally a stage 3 or type C, where a true dislocation can be obserced. In the type C, often the cruciate ligamanets are abscent or defiscient.
There maybe a role for arthrography especially when conservative treatment has failed to align the distal femeur and the proximal tibia. The test become very helpful in guiding in further management during a surgical correction.(Curtis 1969, Haga 1997, Ko 1999).
Neibauer (1960) and Curtis (1969) Classification
As I already pointed out, the treatment of a congenital knee dislocation starts at the Nursery. The grade I and the grade 2 can be treated non operatively with serial of cast or splint. Occasionally supplemental skin traction may be needed. It is believed that treatment applied less than 20 hours after birth should bring the best results. We generally attempt to flex the knee to a 90-degrees of flexion but often we have to accept at the beginning the maximum flexion allowed during the examination. Orthopedist uses splint, Pavlick harness to maintain the reduction. In presence of quadriceps contracture, nowadays some may use botulinum toxin injection to assist in the progressive stretching of the quadriceps muscles (Extensor mechanism), achieving the required flexion. (Kaissi 2011).
Pavlick Harness in the treatment of congenital knee dislocation (CKD)
If casting pr splinting treatment fails to correct the knee flexion, quadriceps lengthening may be necessary and it may be necessary to perform as well as the lengthening of some parts of the hamstrings, the iliotibial band and the knee capsule. The cruciate ligaments may need to be reconstructed or advanced (Curtis 1969, Neibauer 1960, Ooishi 1983, Johnson 1987, Ko 1999). It is now described in the literature another reason for the hyperextension pointing toward a long-term quadriceps insufficiency suggesting the need for a lengthening procedure of the extensor mechanism (Johnston 2011, Sud 2009, Oetgen 2010). Posterior capsulotomies and capsulorrhaphies may be also needed. In a skeletally mature knee, a dislocation of the knee has more repercussions and immediate consequences like a thrombose or a section of the neurovascular bundle (Popliteal vessels)..
Presently, orthopedist have a tendency in staying away from procedure like femoral osteotomies for shortening procedures. Performing a mini-open or a percutaneous Clubfoot correction and casting can be also carried out while casting for Quadricepsplasty. (Abdelaziz 2011, Shah 2009). Surgeons have also performed concomitant hip or foot surgery to correct other deformities in one sitting in the operating room to avoid a return to the operating room. Casting for clubfoot deformity can be also performed while the knee is kept in flexion for a case of congenital knee dislocation.
A congenital knee dislocation (CKD) in the stages 1 and 2 is more often treated non-operatively but in the stage 3, better results are obtained with orthopedic surgical procedures performed by skilled orthopedist. Some suggest the use traction prior to casting in order to avoid the long-term effects of the illio-tibial band. Rubbing on the epiphysis, especially a deformity (Lawrence 1967, Curtis 1969). Residual hyperextension may be encountered. Quadriceps insufficiency may be also seen as a complication of the shortening procedures (Oetgen 2010).
So, the treatment options rest with serial of casting with increasing knee flexion in stage 1 and 2. One can opt to use a Pavlick harness like we do with baby with developmental hip dysplasia. Occasionally both pathologies can be associated with feet deformity.
If the conservative efforts fail to relocate the knee, especially in the stage 3, a surgical reconstruction is the rule with Quadricepsplasty through an open procedure or through a mini-incision for a quadriceps recession. Attention must be given to the quadriceps muscles, the hamstring muscles, the iliotibial band, the capsule and the cruciate ligaments may need to be reconstructed as well. In fact, all structures able to jeopardize the range of motion of the congenital dislocated knee.
I wish the best of luck to my orthopedic residents and colleagues and to ail who generally take care of newborns so such pathology will not be missed. This will avoid surgical interventions more detrimental to the knee of the newborn.
Maxime Coles MD
Boca Raton FL
1- S.Schreiner, R. Ganger, F Grill : Congenital knee joint dislocation (CDK): The Orthopedist Volume 41,(1) January 2012pp 55-82.
2- Congenital dislocation of the knee: journal of bone and Joint surgery. American. Volume 42-A. March 1960, pp 1207-225.
3- K Jacobsen, F Vopalecky: Congenital dislocation of the knee. Acta Scandinavia. Volume 56(1) February 1885, pp 1-7.
4- K Parsch, RD Schultz: Ultrasonogrphy in congenital knee dislocation, 1994. Journal of Pediatric Orthopedics. (B) 3: pp 76-81.
5- Baldwin CH: Congenital Dislocation of the Knee Joint. J Bone Joint Surg Am 1926 Oct 8(4): pp 822-823.
6- Curtis BH, Fisher RL: Congenital hyperextension with anterior subluxation of the Knee. J Bone Joint Surg Am. 1969 Mar, 51(2):pp 255-269.
7- Drennan JC. Congenital Dislocation of the knee and patella. Instr Course Lect 1993; 42:pp 517-524.
8- Elchalal U and al. Antenatal Diagnosis of Congenital Knee Dislocation: a case report. Am J Prenatal. 1993 May; 10(3) pp 194-196.
9- Haga N, et al: Congenital dislocation of the knee reduces spontaneously or with minimal treatment. J pediatr Orthop. 1997 Jan; 17(1) pp 59-62.
10- Johnson K, Vopalecky F, Congenital Dislocation of the knee. Acta Orthop Scand. 1985 Feb; 56(1): pp 1-7.
11- Mawrence M; Genu RecurvatumCongenitum. J Bone Joint Surg Br 1967 Feb; 49(1): pp 1231-134.
12- Sua A et al. Functional outcomefollowing quadriceps tendon lengthning in congenital dislocation of the knee, with reference to extensor weakess. Strategies Trauma Limb Reconstr 2009 Dec; 4(3): pp 123-127.