Figure 197-1 Schematic of long bone structure.
Neurologic maturation, marked by achievement of developmental motor milestones, is important for normal musculoskeletal development (see Section 2). A neurologic disorder may cause a secondary musculoskeletal abnormality (e.g., extremity contractures in Duchenne muscular dystrophy). Thus, normal motor development must be included in the definition of a normal musculoskeletal system.
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In-Toeing, Out-Toeing, and Toe-Walking Bowlegs and Knock-Knees
The in utero position of the fetus can affect the angular and torsional alignment (temporary or permanent) of the skeletal system, especially of the lower extremity (Fig. 197-3). The newborn’s hips are externally rotated. Pes planus and genu varum are common. Infants are usually born with a flexed posture. This position usually decreases to neutral within the first 4 to 6 months. The foot is often flat and tucked under at birth; the ankle will be inverted and the forefoot is adducted when compared with the hindfoot. The lateral border of the foot must straighten out, even with dorsiflexion, to be considered secondary to in utero positioning.
The head and neck may also be distorted by in utero positioning. The spine and upper extremities are less likely to be affected. By the age of 3 to 4 years, the effects of in utero positioning have usually resolved.
Normal gait has a stance phase and swing phase; each legshould have symmetrical timing with each phase. The
Figure 197-2 The ends of long bones at various ages. Lightly stippled areas represent cartilage composition, whereas heavily darkened areas are zones of ossification. (From Tachjidan MO: Congenital Dislocation of the Hip, New York, 1982, Churchill Livingstone, p 105.) stance phase represents 60% of the gait and begins with footcontact (usually the heel strike) and ends with the toe-off.During the swing phase (40%), the foot is off the ground.The gait cycle is the interval between stance phases on thesame limb.
Toddlers will generally walk independently by 18 months of age. Their externally rotated gait is usually inconsistent, is characterized by short, rapid steps, and does not have the reciprocal arm swing. Gait coordination improves over time, with a normal gait usually achieved by the time a child enters elementary school.
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Limp In-Toeing, Out-Toeing, and Toe-Walking
The Limping Child
The differential diagnosis for a limping child is often categorized by age and presence or absence of a painful limp (Table 197-3). The gluteus medius muscle stabilizes thepelvis during the stance phase, preventing the pelvis fromdropping toward the leg in swing phase. An antalgic gait is a painful limp; the stance phase and stride of the affected limbare shortened to decrease the discomfort of weight bearingon the affected limb. The Trendelenburg gait has a normal stance phase, but excessive swaying of the trunk. Waddling gait refers to a bilateral decrease in function of the gluteusmuscles.
Toe walking is a common complaint in early walkers. A physician should evaluate any child older than 3 years of age whostill toe walks. Although this is most likely habit, a neuromuscular disorder (cerebral palsy, tethered cord), Achilles tendoncontracture (heel cord tightness), or a leg-length discrepancyshould be considered.
Differential Diagnosis of Limping in Children
Early walker: 1 to 3 years of age
Child: 3 to 10 years of age
Developmental dysplasia of the hip Neuromuscular disorder Cerebral palsy Lower extremity length inequality
Septic arthritis, osteomyelitis, myositis Transient monarticular synovitis Trauma Rheumatologic disorders