What is hyperextension of a limb as a congenital condition?

Hyperextension of a Limb as a Congenital Condition

Congenital hyperextension of a limb refers to an abnormal excessive extension of a joint beyond its normal range of motion, present at birth, which can range from mild hyperextension to complete dislocation.1, 2

Definition and Classification

• Congenital hyperextension, also known as genu recurvatum when affecting the knee, is a rare condition representing approximately 0.45% of all congenital anomalies 1
• This condition belongs to a broader category of congenital limb deficiency disorders (LDDs), which are characterized by aplasia (absence) or hypoplasia (underdevelopment) of bones in the limbs 3
• Limb deficiencies are classified as either transverse (due to intrauterine disruptions of previously normal limbs) or longitudinal (isolated or associated with certain syndromes and chromosomal anomalies) 3

Clinical Presentation

• The condition presents with abnormal hyperextension of the affected joint, most commonly the knee, with significant limitation of flexion 2
• In severe cases of knee hyperextension (genu recurvatum), the deformity can reach approximately 30 degrees of hyperextension 1
• Isolated hyperextension is extremely rare, as approximately 60% of cases are associated with other congenital anomalies, with congenital hip dislocation being the most common associated condition 1

Causes and Pathophysiology

• The etiology is multifactorial and may include:
  • Vascular disruption during embryonic limb formation or in already-formed fetal limbs 4
  • Mechanical factors such as abnormal positioning in utero 4
  • Genetic factors in some cases, particularly when associated with syndromes 3
• The timing of vascular disruption during pregnancy correlates with the severity of the defect - earlier disruptions (before 68 days' gestation) tend to cause more severe and proximal defects 5

Diagnosis

• Diagnosis is primarily clinical, based on physical examination showing the hyperextension deformity 1
• Radiological confirmation is important to assess the extent of the condition and rule out other skeletal abnormalities 1
• A complete physical examination is necessary to identify whether the condition is isolated or part of a syndromic presentation 5
• Genetic consultation is advisable, especially when multiple anomalies are present 3

Treatment and Prognosis

• Early recognition and immediate intervention through gentle manipulation, passive stretching, and flexion exercises can completely correct the deformity without surgery in many cases 1
• Treatment should begin in early infancy, with hand orthoses for upper limb involvement to limit muscle contraction and joint malposition 6
• Surgical intervention may be required in more severe or resistant cases to release contractures and restore muscle balance 6
• With appropriate care, most children with limb deficiencies can lead productive lives 3
• Long-term care should occur in specialized limb deficiency centers with expertise in orthopedics, prosthetics, and occupational and physical therapy 3

Associated Conditions

• Congenital hyperextension may be part of more complex conditions such as:
  • Limb overgrowth disorders 7
  • Congenital muscular hypertrophy 6
  • Developmental dysplasia of the hip (DDH) 4

Follow-up and Monitoring

• Regular follow-up is essential to monitor the progress of treatment and detect any complications 1
• In successfully treated cases, normal movement of the affected limb can be achieved, as confirmed by clinical and radiological evaluation 1