What is the appropriate management for a newborn with mobile knees?

Management of Mobile Knees in a Newborn

All newborns with mobile knees (suspected congenital knee dislocation) require immediate clinical classification based on reducibility to guide treatment, with most cases responding to conservative management when initiated early. 1

Immediate Clinical Assessment

Classify the knee dislocation neonatally using the three-type system based on reducibility and stability:

• Type I (Reducible): Knee reduces easily with a palpable snap when femoral condyles pass in flexion and remains stable in flexed position 2, 3
• Type II (Recalcitrant): Knee reduces with posteroanterior "piston" pressure but is unstable, with iterative dislocation once pressure is released 2, 3
• Type III (Irreducible): Knee cannot be reduced by manual manipulation 2, 3

Document the number of anterior skin grooves, baseline range of motion, flexion deficit, and reduction stability, as these correlate with severity and prognosis 2, 3

Diagnostic Workup

Refer immediately to a specialist center for comprehensive evaluation, as skeletal dysplasias require multidisciplinary assessment regardless of prenatal diagnosis. 1

• Perform clinical examination and skeletal radiographic surveys to establish specific diagnosis 1
• Pursue appropriate molecular testing where applicable, as early accurate diagnosis allows institution of specific therapies and anticipatory screening for associated comorbidities 1
• Evaluate for associated conditions including hip dysplasia, clubfoot, and other skeletal abnormalities that commonly occur with congenital knee dislocation 4, 2

Treatment Algorithm Based on Classification

Type I (Reducible) Knees

• Initiate physiotherapy with splinting immediately, which achieves stable reduction in all Type I cases without need for surgery 2
• Maintain knee in flexed, reduced position using splints 2
• Expected outcome: 82% achieve good or excellent results 2

Type II (Recalcitrant) Knees

• Begin with physiotherapy and splinting 2
• If unsuccessful, progress to traction with cast immobilization (required in 31% of Type II cases) 2
• Surgery is rarely needed for Type II knees 2
• Expected outcome: 68% achieve good results 2

Type III (Irreducible) Knees

• Surgical intervention is required in 57% of Type III cases 2
• Surgery should be performed at a specialist center with expertise in skeletal dysplasias 1
• Expected outcome: All Type III knees have poor outcomes, emphasizing the importance of early recognition and treatment 2

Critical Management Principles

Treatment must begin while the patient is still young to prevent deformity from becoming established and irreversible. 5

• Start treatment as soon as practical after delivery, ideally within the first week of life when mean age at first consultation is 5.6 days 2, 3
• Do not delay treatment while awaiting definitive diagnosis, as early intervention significantly influences long-term joint function and patient outcomes 1, 4
• Ensure access to multidisciplinary team including orthopedics, genetics, pediatrics, and physical therapy 1

Specialist Referral Benefits

Referral to a specialist center provides: establishment of specific diagnosis, delineation of natural history, institution of specific therapies (such as enzyme replacement therapy for hypophosphatasia), anticipatory screening for associated comorbidities (sleep apnea, hearing loss, renal failure), accurate genetic counseling for recurrence risks, and appropriate postnatal management. 1

Prognostic Factors

The severity of neonatal presentation directly correlates with treatment requirements and outcomes, with increasing rates of surgical indication and decreasing rates of satisfactory outcomes from Type I to Type III 2

Number of anterior skin grooves, baseline flexion, and range of motion are greater in Type I than Types II and III, serving as useful prognostic indicators 2, 3