Approach to the child with knock-knees
- Scott B Rosenfeld, MD
Scott B Rosenfeld, MD
- Assistant Professor of Pediatric Orthopaedic Surgery and Scoliosis
- Baylor College of Medicine
- Section Editors
- William Phillips, MD
William Phillips, MD
- Section Editor — Pediatric Orthopedics
- Professor of Pediatrics and Orthopedics
- Baylor College of Medicine
- Teresa K Duryea, MD
Teresa K Duryea, MD
- Section Editor — General Pediatrics
- Associate Professor of Pediatrics
- Baylor College of Medicine
Knock-knees (genu valgum) is an angular deformity at the knee where the apex of the deformity points toward the midline (figure 1). Bow-legs (genu varum) is an angular deformity at the knee where the apex of the deformity points away from the midline.
Bow-legs and knock-knees are among the most common musculoskeletal anatomic variations encountered by pediatric primary care providers and a common reason for referral to a pediatric orthopedic surgeon. However, most children with knock-knees or bow-legs have variations of normal lower-extremity development and can be monitored by the primary care provider.
An understanding of the normal physiologic development of the lower extremity is essential in differentiating physiologic from pathologic alignment. Pathologic causes of knock-knees include posttraumatic (eg, Cozen fracture), rickets (eg, renal osteodystrophy), skeletal dysplasias, mucopolysaccharidosis, and neoplasms. Unlike physiologic knock-knees, these conditions generally do not improve over time and may require treatment with bracing or surgery.
This topic will provide an overview of normal physiologic alignment of the lower extremity, physiologic and pathologic causes of knock-knees, and an approach to the child with knock-knees. Bow-legs are discussed separately. (See "Approach to the child with bow-legs".)
NORMAL PHYSIOLOGIC ALIGNMENT
An understanding of normal physiologic development of the lower extremity is essential to differentiation of physiologic from pathologic deformities. Lower-extremity alignment goes through a predictable progression from varus (bow-legs), to neutral, to valgus (knock-knees), and back towards neutral over the first seven years of life (figure 2 and figure 3) . Final adult lower-extremity alignment is slightly valgus. There is a wide range of normal values [1,2].
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- NORMAL PHYSIOLOGIC ALIGNMENT
- CAUSES OF KNOCK-KNEES
- Physiologic valgus
- Pathologic valgus
- - Posttraumatic
- - Other causes
- CLINICAL PRESENTATION
- Physical examination
- Additional evaluation
- INDICATIONS FOR REFERRAL
- Physiologic knock-knees
- Pathologic knock-knees
- SUMMARY AND RECOMMENDATIONS