Normal Talar–1st Metatarsal Angle Size on Radiography
The talar–1st metatarsal angle (also known as the lateral Meary's angle in adults) describes the longitudinal alignment between the talus and the first metatarsal on a lateral foot radiograph. In the pediatric foot, this angle serves as a key indicator of midfoot sagittal alignment and arch development. Accurate measurement is essential for detecting and monitoring conditions such as flatfoot deformity and cavus foot in growing children.
Normal Reference Values
| Orientation | Age | Measurement |
|---|---|---|
| Lateral | Newborn | 19¡ |
| Lateral | 2 y/o | 21¡ |
| Lateral | 4 y/o | 9¡ |
| Lateral | 4-9 y/o | -7-39¡ |
Clinical Significance
In a normally aligned foot, the long axes of the talus and first metatarsal should be roughly collinear on the lateral projection. Deviation from age-appropriate norms indicates either plantar flexion of the forefoot (positive/plantarward angulation, seen in cavus) or dorsiflexion relative to the talus (negative/dorsalward angulation, associated with flatfoot or rocker-bottom deformity). Because normative values shift substantially during early childhood, age-matched reference data are critical for accurate interpretation.
The wide range seen in the 4–9-year-old cohort (−7° to 39°) reflects the broad physiologic variability during arch maturation. Persistent or progressive plantar angulation beyond expected norms may warrant orthopedic evaluation. Conversely, markedly negative values may suggest a convex pes planus or vertical talus.
- Congenital vertical talus: severely increased plantar angulation of the talus relative to the metatarsal axis
- Flexible flatfoot: mildly negative or borderline values, typically correcting with weight redistribution
- Cavus foot: exaggerated positive (plantarward) angulation of the first metatarsal
- Rocker-bottom deformity: associated with neuromuscular conditions, producing characteristic sagittal malalignment
- Clubfoot (talipes equinovarus): combined coronal and sagittal angular abnormalities affecting this measurement
Reference: Vanderwilde R, Staheli LT, Chew DE et al. Measurements on radiographs of the foot in normal infants and children. J Bone Joint Surg Am. 1988;70(3):407–15.
Imaging Notes
Measurement is performed on a true lateral weight-bearing radiograph of the foot whenever possible, as loading significantly affects midfoot alignment. A line is drawn through the longitudinal axis of the talus and a second line through the longitudinal axis of the first metatarsal shaft; the angle between these two lines is recorded. By convention, plantar angulation of the first metatarsal relative to the talus yields a positive value, while dorsal angulation yields a negative value.
In non-ambulatory infants, a simulated weight-bearing or maximum dorsiflexion lateral view is used as a practical alternative. Strict lateral positioning is essential — even minor rotation introduces significant measurement error. Consistent technique across serial examinations is paramount when monitoring progression or treatment response in pediatric foot deformities.