Crural Index
Definition
The ratio of tibia length to femur length, multiplied by 100. Varies systematically between populations: higher (relatively longer tibia) in tropical populations, lower in higher-latitude populations. The basis for why stature equations derived from one population systematically mis-estimate stature for individuals from a different population.
- Formula
- Tibia length divided by femur length, times 100
- Tropical populations
- Tend toward a higher index (relatively longer tibia)
- Higher-latitude populations
- Tend toward a lower index
- Forensic implication
- Stature equations are population-specific
Common questions
Why does the crural index vary between populations at all?+
Limb proportions track climate adaptation over generations: a relatively longer lower leg increases surface area for heat loss, which is advantageous in warmer climates, while a shorter, stockier build conserves heat in colder ones, and these tendencies are reflected in the tibia-to-femur ratio.
What error results from ignoring the crural index when estimating stature?+
A stature equation built from measurements of one population encodes that population's typical limb proportions. Applying it to skeletal remains from a population with a different crural index systematically over- or under-estimates stature, so equations should be matched to the estimated population affinity of the remains.
Related terms
- Age-Related Stature Loss
- The decrease in living stature with age due to intervertebral disc compression and vertebral remodeling, approximately 0.10-0.12 cm per year after age...
- Auerbach-Ruff 2004 Method
- A body-mass estimation method using bi-iliac (maximum pelvic) breadth combined with stature, providing an alternative proxy when the femoral head is absent...
- Femoral Head Diameter (FHD)
- The superoinferior diameter of the femoral head, measured at the widest point perpendicular to the neck axis. The primary skeletal proxy for...
- Maximum (Anatomical) Femur Length
- The bone length measured from the most superior point of the femoral head to the most inferior point of the femoral condyles...
- Mukherjee-Bandyopadhyay Equations
- Population-specific stature regression equations for Bengali Indian males and females, published in 1955 from cadaveric material at Calcutta Medical College. The male...
- Ruff-Scott-Walker 1997 Method
- The principal body-mass estimation method from skeletal remains, using femoral head diameter (and, in the Auerbach-Ruff 2004 extension, bi-iliac breadth combined with...
- Standard Error of Estimate (SEE)
- The statistical uncertainty around a regression-based stature estimate, representing the range within which approximately 68 per cent of individuals in the derivation...
- Stature Regression Equation
- A mathematical equation derived from a reference skeletal sample with known stature and long-bone measurements, used to estimate living stature from measured...
- Trotter-Gleser Equations
- The foundational US stature regression equations published by Mildred Trotter and Goldine Gleser in 1952 (from WWII casualties) and revised in 1958...