Congenital knee deformity: rare case report and unexpected finding in the delivery room
Highlight box
Key findings
• A full-term female newborn presented at birth with bilateral passive fixed hyperextension of the knees and limited flexion, with otherwise normal systemic, musculoskeletal, and neurovascular examination.
• The diagnosis of congenital knee dislocation (CKD) (genu recurvatum) was confirmed, and the patient was managed with knee reduction manipulation and serial casting with ongoing radiographic follow-up.
What is known and what is new?
• CKD is a rare condition characterized by hyperextension of the knee with limited flexion. It may occur as an isolated finding or in association with other conditions and is commonly treated conservatively during infancy using manipulation and serial casting without surgical intervention.
• This article reports a bilateral case recognized immediately in the delivery room, with normal radiographic findings and no associated musculoskeletal abnormalities, highlighting early diagnosis and conservative management.
What is the implication, and what should change now?
• Early recognition of CKD is essential to enable prompt management and improve outcomes.
• Careful clinical assessment at birth and timely orthopedic referral should be emphasized to initiate early conservative treatment and prevent long-term functional impairment.
Introduction
Congenital knee dislocation (CKD), or genu recurvatum, is an uncommon congenital deformity. It is characterized by hyperextension of the knee greater than 0° with limited flexion, increased transverse skin folds over the anterior surface of the knee, and protrusion of the femoral condyles into the popliteal fossa (1). It may present alone or associated with other conditions, such as Down syndrome, Turner syndrome, arthrogryposis multiplex congenita, Larsen syndrome, and Ehlers-Danlos syndrome (2,3). It may also be associated with other congenital musculoskeletal abnormalities, such as developmental dysplasia of the hip, talipes equinovarus (4,5), congenital elbow dislocation, and various foot deformities (6).
The incidence of CKD is 1 per 100,000 live births (7), with more incidence in females, with no significant difference between the right and left knees. Bilateral CKD has been reported in one-third of the cases (3), with no predominance observed in any specific geographic region (8). Although a familial pattern suggests a possible hereditary component, the exact genetic factors are not yet defined (9). The pathogenesis and etiology of CKD remain unclear; however, several predisposing factors have been identified, including intrinsic causes such as genetic abnormalities and complex anomalies, as well as extrinsic factors, such as breech presentation, oligohydramnios, and compression, which may contribute to the etiology (6,9,10).
CKD can be classified into two types (11): malformative, associated with abnormalities of the elastic tissues, and postural, resulting from abnormal fetal positioning or oligohydramnios. It can also be classified according to the postnatal spectrum of this condition into three different phenotypes: simple hyperextension of the knee joint (Type 1), anterior subluxation (Type 2), and anterior luxation of the tibia relative to the femoral bone (Type 3) (10).
CKD can be diagnosed pre-natally or post-natally (3,6,12). The prenatal diagnosis of this condition has not been described extensively, with the first in-utero diagnosis reached using X-ray in 1986 (13). It has been reported that the diagnosis of CKD can be confirmed by prenatal ultrasound at approximately 20 weeks of gestation (14,15). Diagnosis can be confirmed clinically by the presence of a backward-bending knee, a dimple or crease over the anterior aspect of the knee, and the absence of a suprapatellar pouch (16). However, limb radiography is needed to confirm subluxation or dislocation. Early recognition and timely intervention are crucial to prevent long-term complications. Complications of CKD, if left untreated, include the development of stiffness or instability and variable degrees of functional impairment in the knee (15).
Most of the cases are treated during infancy by manipulation and serial casting or splinting without surgical intervention (7). However, the existing literature on CDK is limited, and there is a lack of comprehensive guidance on optimal treatment approaches. Current literature describes contradictory findings as a result of using different management strategies. We report a case of a female newborn with bilateral CKD, recognized and diagnosed in the delivery room. This case report aims to enhance the understanding of this condition and its associations, improving the process of early diagnosis and management to prevent long-term functional impairment. We present this article in accordance with the CARE reporting checklist (available at https://acr.amegroups.com/article/view/10.21037/acr-2026-0114/rc).
Case presentation
Patient demographics
We present a case of a full-term female newborn born via lower segment caesarean section (LSCS) to a 28-year-old G3P1A1 (gravida 3, para 1, abortus 1) healthcare professional Emirati patient. She got married 3.5 years ago with no consanguinity to her husband.
Obstetric history
Her first pregnancy was spontaneous, which ended with a missed miscarriage at 9 weeks of gestational age. After which, she underwent an evacuation of retained products of conception. The second pregnancy was through in vitro fertilization in 2022. It was a singleton pregnancy with cephalic presentation, and a male newborn was delivered in 2023 via emergency grade two low-segment caesarean section for failure to progress, with a birth weight of 3.6 kg.
Medical and surgical history
Medical history includes spondylolisthesis of the L5 vertebra over S1 and post-pseudo-disc herniation at the L5–S1 level. Her family history is significant for diabetes on her maternal side. She has no known drug allergies. Additionally, her past surgical history is significant for a fibroadenoma resected through bilateral breast lumpectomy.
Current pregnancy course
The last pregnancy occurred spontaneously 5 months post her last childbirth during lactational amenorrhea, and the estimated date of delivery was 21/02/2025. It was complicated by iron deficiency anemia, frequent micturition, vulvovaginitis, and gestational diabetes mellitus, which was controlled by 750 mg metformin. Her antenatal blood tests and other laboratory investigations were within normal limits, with negative maternal serology and a negative group B streptococcus (GBS) screen. A nuchal translucency scan was performed during the 1st trimester, showing a nuchal translucency thickness of 1.4 mm with a combined screening low risk of 1:4,500. The anomaly scan and the growth scan were also within normal limits. The growth scan, which was done in the third trimester, revealed a frank breech presentation with a posterior high placenta and an estimated fetal weight corresponding to the gestational age appropriately. The biophysical profile, amniotic fluid volume, and umbilical artery pulsatility index (PI) parameters were within normal limits.
Delivery details
The mother developed preterm labor and was admitted at 35 weeks gestational age in another facility, where she received a two-dose regimen of steroid injections and tocolysis. Then she was referred to our facility for elective LSCS, which was scheduled at 38+4 weeks. The surgery proceeded without complications, and maternal progress and outcomes were uneventful.
Neonatal findings
The birth weight of the newborn was 3.21 kg, and the Appearance, Pulse, Grimace, Activity, and Respiration (APGAR) score was 9 and 10 at 1 and 5 minutes, respectively. However, a deformity was noticed at birth. The systemic examination of the baby was ordinary, but the initial physical examination at birth was remarkable for bilateral passive fixed hyperextension of the knees and limited flexion with a full range of motion (Figure 1). Both Barlow and Ortolani hip tests were negative. The patient’s neurovascular status was intact in the lower extremities bilaterally, and the remainder of the musculoskeletal examination was normal as well.
Investigation and management
An X-ray and ultrasound of both the hip and knee joints were requested, accompanied by an orthopedic consultation. Radiography of the right knee was negative for fracture or other acute pathology. Based on the neonatal findings and subsequent clinical course, there was no documented evidence of anterior tibial displacement, tibiofemoral subluxation, or irreducible dislocation. Therefore, the diagnosis of CKD was confirmed and classified as CKD/simple hyperextension (Grade I congenital knee deformity), rather than congenital knee subluxation (Grade II) or CKD (Grade III).
Following diagnosis, the neonate was referred to the pediatric orthopedic team and managed with gentle passive stretching and progressive correction of the knee hyperextension deformity. Serial splinting and casting were initiated during infancy, with the knee gradually positioned in increasing degrees of flexion at each treatment stage. Regular outpatient follow-up was performed to assess correction of the deformity, skin integrity, neurovascular status, range of motion, and overall lower limb development. Treatment was continued until satisfactory knee alignment and function were achieved. The patient subsequently underwent long-term orthopedic follow-up, with complete clinical resolution reported after approximately 1 year of conservative management (Figure 2). The patient is walking normally with no pain or progressive deformity; however, a small degree of hyperextension remains. All procedures performed in this case were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Declaration of Helsinki and its subsequent amendments. Written informed consent was obtained from the parents of the patient for publication of this case report and accompany images. A copy of the written consent is available for review by the editorial office of this journal.
Discussion
We report a case of a full-term female newborn who was noted at birth to have bilateral passive fixed hyperextension of the knees and limited flexion with a full range of motion, and a diagnosis of CKD was confirmed. Examination of the musculoskeletal and neurovascular status in both lower limbs was normal. Radiography of the right knee was negative for fracture or other acute pathology, and both the Barlow and Ortolani hip tests were negative. The pregnancy was complicated by iron deficiency anemia, frequent micturition, vulvovaginitis, and gestational diabetes mellitus. The patient underwent knee reduction-manipulation and received serial casting and repeated radiographic evaluation for improvement. After 1 year of conservative treatment, the patient exhibited an excellent prognosis and is now walking normally without pain or progressive deformity; however, a small degree of hyperextension remains.
Castro-Lara et al. reported a more severe case of CKD in a full-term female newborn, in which the patient had a unilateral congenital dislocation of the left knee, characterized by pronounced hyperextension (CKD), with passive flexion allowing only partial, incomplete correction (6). Additionally, an X-ray of the left knee revealed an anterior displacement of the tibia relative to the femoral condyles. These results contradict our findings, in which the patient presented with bilateral passive fixed hyperextension of the knees, with normal radiographic findings. While the pregnancy in our case was complicated by iron deficiency anemia, frequent micturition, vulvovaginitis, and gestational diabetes mellitus, the pregnancy in the case reported by Castro-Lara et al. was well controlled, with no associated maternal comorbidities, no exposure to teratogenic medications, and no recorded perinatal complications (6). Worku et al. and Wilebski et al. also reported more severe cases of CKD associated with subluxations or dislocations (4,9). However, both cases were unilateral, unlike our case, in which the patient had bilateral CKD.
Godwin Joy reported two cases of full-term female infants with Grade 3 isolated unilateral CKD (5). On examination, the knees of both babies were in 90 degrees and 20 degrees of hyperextension. Additionally, the Ortolani and Barlow tests of the lower limbs were normal. The patients were conservatively managed with serial casting and a 4-weekly manipulation, with an overall improvement in functionality over a period of 3 months, according to the Modified Knee Functional Scoring System (4). These findings are similar to ours, in which the Ortolani and Barlow tests of the lower limbs were normal, and the patient was managed conservatively, resulting in functional improvements. Ramachandran and Baalann also reported a case of CKD in a newborn, which was treated with manipulation and serial correction with Plaster of Paris application (17). This treatment approach led to significant functional improvements, which highlights the significance of conservative management in achieving favorable results. A summary of related case reports is shown in Table 1.
Table 1
| Study | Neonate sex | Laterality | Severity/type | Prenatal detection | Associated anomalies | Imaging findings | Management | Outcome/follow-up |
|---|---|---|---|---|---|---|---|---|
| Castro-Lara et al. [2026] (6) | Female | Unilateral (left) | Grade III knee dislocation | No | None | X-ray: anterior tibial displacement | Reduction + plaster splint | Normal range of movement and gait at 5 months |
| Worku et al. [2025] (9) | Female | Unilateral (left) | Knee dislocation | No | None | X-ray confirmed dislocation | Reduction + serial long-leg casting | Normal range of movement at 12-week follow-up |
| Wilebski et al. [2024] (4) | Male | Unilateral (left) | Knee dislocation/subluxation (~45°) | No | None | Radiograph: anterior tibial translation | Non-surgical reduction + serial casting | Excellent outcome after 3 months |
| Qi et al. [2024] (14) | Female | Unilateral (right) | Type II knee dislocation | No | Bilateral hip dislocation, congenital heart disease (ASD) | US, X-ray, MRI confirmed | Surgery (V-Y quadriceps lengthening) + casting | Walking independently at follow-up |
| Joy [2024] (5) | Female (2 cases) | Unilateral (left) | Grade III genu recurvatum | No | None | Radiography confirmed | Serial manipulation + casting | Functional improvement at 3 months |
| Palco et al. [2022] (15) | Female | Bilateral | Knee hyperextension (30–45°) | No | Bilateral calcaneovalgus feet | Clinical diagnosis | Reduction + serial casting | Complete correction by 3 months |
| Ramachandran et al. [2022] (17) | NR | NR | Congenital genu recurvatum | No | NR | NR | Serial manipulation + plaster casts | Correction after 17 weeks |
| Salguero-Sánchez et al. [2022] (8) | Female | Bilateral | Grade III knee dislocation | No | Genu valgum, flat feet | Clinical diagnosis | Manual reduction + bilateral casts | Progressive correction |
| Yeoh et al. [2021] (2) | Female | Unilateral (right) | Type II knee dislocation (~50° hyperextension) | No | None | X-ray: hyperextension with anterior subluxation | Casting after failed Pavlik harness | Normal development at 24 months |
| Morales-Roselló et al. [2020] (12) | Female | Bilateral | CKD | Yes (US + MRI) | Right hip subluxation | MRI: tibial anterior translation | Manual reduction + casts + Pavlik harness | Progressive improvement at 3 months |
| Ogbonna [2018] (16) | Female | Bilateral | Congenital genu recurvatum (~45°) | Oligohydramnios noted | None | Imaging not performed | Referred to orthopedics | No treatment (left against advice) |
| Shah et al. [2012] (18) | Female | Unilateral (left) | Knee dislocation | No | None | X-ray: anterior tibial dislocation | Manipulation + above-knee POP slab | Normal knee at 3–6 months |
| Agbeko et al. [2011] (19) | Female | Bilateral | Genu recurvatum with bilateral hip dislocation | No | Camptodactyly, cleft palate, bilateral hip dislocation | Hip US: bilateral hip dislocation | Orthopedic treatment for hips | Referred to surgical ward |
| Gorincour et al. [2003] (20) | Male | Unilateral (left) | Congenital genu recurvatum | Yes (24-week US) | None | Radiographs confirmed CGR | Manipulation + serial splinting | Improved mobility at 10 months |
ASD, atrial septal defect; CGR, congenital genu recurvatum; CKD, congenital knee dislocation; MRI, magnetic resonance imaging; NR, not reported; POP, plaster of Paris; US, ultrasound.
Chatelaine was the first to describe CKD in 1822, and later by Bord in 1834 (6). Its incidence is estimated to be 1 per 100,000 live births (7). The pathogenesis and etiology of CKD remain unclear; however, several predisposing factors have been identified, including intrinsic causes such as genetic abnormalities and complex anomalies, as well as extrinsic factors. such as breech presentation, oligohydramnios, and compression, which may contribute to the etiology. This is believed to result from a “packaging syndrome”, which can lead to knee dislocation (6,21). While intrinsic causes involve muscular abnormalities that result in joint and bone deformities. Such manifestations are commonly observed in genetic or congenital syndromes, for example, arthrogryposis, myelomeningocele, and Down syndrome. The latest growth scan report done for our case at the third trimester revealed a frank breech presentation, which can be considered a risk factor for this condition according to previous studies. Otherwise, the mother’s clinical history has no established risk factors for this condition. Cavoretto et al. (10) conducted a systematic review that included 20 cases, in which 55% of the cases were bilateral, and 35% of the cases were unilateral and associated with other anomalies in 65% of the cases. Additionally, they reported an association with oligohydramnios in 20% of the cases, whereas in 65% of the cases, an invasive procedure was performed. Genetic syndrome was present in 77% of bilateral cases.
CKD has three severity grades: congenital hyperextension of the knee (congenital genu recurvatum) (Grade 1), congenital hyperextension with anterior subluxation of the tibia over the femur (Grade 2), and congenital hyperextension with anterior dislocation of the tibia over the femur (Grade 3) (6). Clinical evaluation should assess the reducibility of the hyperextension, the stability of the femoral condyles during flexion, the number of anterior transverse skin creases, and the range of motion (3). Radiological evaluation should include anteroposterior (AP) and lateral radiographs obtained in both flexion and maximal extension. These classifications are critical to direct treatment options as well as prognosis.
Treatment of this condition includes physiotherapy, conservative non-surgical management, and surgical open reduction. An orthopedic consultation and reduction are essential and should be conducted as early as possible to prevent the development of soft tissue contractures. The aim is to progressively improve knee flexion while maintaining the reduction, with the duration of application varying as needed. Our case underwent knee reduction-manipulation and is currently on serial casting, showing positive outcomes.
Clinical implications
This case highlights the importance of thorough neonatal musculoskeletal examination for the early detection of rare congenital deformities such as CKD. Prompt recognition at birth allows for timely orthopedic referral and initiation of non-surgical management, which can significantly improve functional outcomes and prevent long-term deformities. Infants with CKD should be promptly recognized and referred for multidisciplinary management involving orthopedics and pediatrics. In isolated cases, conservative orthopedic treatment, such as serial casting, corrective splinting, physiotherapy, bracing, and gait training, is generally preferred.
Strengths and limitations
Limitations of this case report include a lack of long-term follow-up, an inability to establish causation, and a lack of ability to generalize. Additionally, this case was managed retrospectively; hence, some technical details of cast positioning and cast-change intervals were not available in the medical record. This case report still has strengths, including its educational value, providing more understanding of a rare, poorly understood condition, the comprehensive clinical history obtained, and the adequate diagnostic investigations performed for both the mother and the child.
Conclusions
This case report study presents a rare case of congenital genu recurvatum in a female newborn, which was noticed immediately after delivery in the delivery room. Early diagnosis is critical to obtain more effective treatment and a more favorable prognosis. Management of this condition should be individualized according to the status of the joint and the presence of other conditions.
Acknowledgments
None.
Footnote
Reporting Checklist: The authors have completed the CARE reporting checklist. Available at https://acr.amegroups.com/article/view/10.21037/acr-2026-0114/rc
Peer Review File: Available at https://acr.amegroups.com/article/view/10.21037/acr-2026-0114/prf
Funding: None.
Conflicts of Interest: Both authors have completed the ICMJE uniform disclosure form (available at https://acr.amegroups.com/article/view/10.21037/acr-2026-0114/coif). The authors have no conflicts of interest to declare.
Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this case were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Declaration of Helsinki and its subsequent amendments. Written informed consent was obtained from the parents of the patient for publication of this case report and accompany images. A copy of the written consent is available for review by the editorial office of this journal.
Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.
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Cite this article as: Almheiri S, Musa A. Congenital knee deformity: rare case report and unexpected finding in the delivery room. AME Case Rep 2026;10:149.
