Protocol - Height - Knee Height

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Protocol Name from Source:

1988-1994 NHANES Body Measurements Protocol


Publicly available


Knee height is measured as the distance from the surface over the femoral condyles to the heel, with the knee flexed to approximately 90 degrees. This measure is used for individuals who are 60 years of age or older, who are unable to stand, or who have spinal deformities. It may be necessary to take replicate measurements.


Knee height was measured on adults 60 years of age and older during National Health and Nutrition Examination Study III, 1988-94. Measurements are taken in the seated position with both legs dangling. The examiner places the fixed blade of the large sliding caliper under the heel of the right leg just below the lateral malleolus of the fibula. From a squatting position, the examiner raises the leg so that the knee and ankle are both at a 90-degree angle (see Exhibit 1). This is best accomplished by resting the participant’s foot in the palm of the examiner’s hand. The moveable blade of the caliper is placed on the anterior surface of the right thigh, above the condyles of the femur, about two inches above the patella. The shaft of the caliper is held parallel to the shaft of the tibia so that the shaft of the caliper passes over the lateral malleolus of the fibula and just posterior to the head of the fibula. Pressure is applied to compress the tissue. The recorder checks the positioning of the leg and the caliper. Knee height is recorded to the nearest 0.1 cm.


Exhibit 1. Proper Positioning of the Participant for the Knee Height Protocol

Personnel and Training Required

Technicians should be trained in the basic techniques of anthropometric measurements and specifically in using calipers.

Equipment Needs



Requirement CategoryRequired
Average time of greater than 15 minutes in an unaffected individualNo
Major equipmentNo
Specialized requirements for biospecimen collectionNo
Specialized trainingNo

Mode of Administration


Life Stage:


Specific Instructions:

Three measurement protocols (Standing Height, Recumbent Height, and Knee Height) accommodate various groups of participants. Self-Reported Height should be used as a last resort only. Several overarching, critical issues for high-quality data collection of anthropometric measures that optimize the data in gene-environment etiologic research include (1) the need for training (and retraining) of study staff in anthropometric data collection; (2) duplicate collection of measurements, especially under field conditions; (3) use of more than one person for proper collection of measurements where required; (4) accurate recording of the protocols and the measurement units of data collection; and (5) use of required and properly calibrated equipment.

The notion of recommending replicate measurements comes from the reduction in random errors of measurement and accompanying improved measurement reliability when the mean of multiple measurements is used rather than the a single measurement. This improvement in measurement reliability, however, depends on the reliability of a single measurement in the hands of the data collectors in a particular study (Himes, 1989). For example, if a measure such as standing height in a given study has a measurement reliability of 0.95 (expressed as an intraclass correlation coefficient), taking a second measurement and using the mean of the two measurements in analyses will improve the reliability to only 0.97, yielding only a 2% reduction in error variance for the additional effort. If, in the same study, the reliability of a single triceps skinfold measurement was 0.85, using the mean, including a replicate measurement, would raise the reliability to 0.92 and yield a 7% reduction in error variance, more than a three-fold improvement compared with recumbent length. Because the benefits of taking replicate measurements are so closely linked with the existing measurement reliability, it is recommended that as a part of the training of those who will be collecting anthropometry data, a reliability study be conducted that will yield measurement reliability estimates for the data collectors, protocols, settings, and participants involved in that particular study (Himes, 1989). If the measurement reliability for a single measurement is greater than or equal to 0.95, the recommendation is that replicate measurement are not necessary and will yield little practical benefit. If the measurement reliability is less than 0.95, the recommendation is to include replicate measurements as prescribed.

If replicate measurements are indicated because of relatively low reliability, a second measurement should be taken, including repositioning the participant. A third measurement should be taken if the first two measurements differ by more than 1.0 cm. If it is necessary to take a third measurement, the two closest measurements are averaged. Should the third measurement fall equally between the first two measurements, all three should be averaged.

Height Prediction

The PhenX Expert Review Panel recommends applying the height prediction equations published by Chumlea and colleagues (1998) based on U.S. national data. The equations are presented separately by gender and race/ethnicity groups for U.S. adults 60 years of age or older.

Height prediction equations using measured knee height differ considerably by gender, age, and race/ethnicity groups because of the different relative proportions of limb segments and height. Accordingly, for applications in other populations, especially those outside of the United States, appropriate equations should be identified for height estimation.

Research Domain Information

Release Date:

October 1, 2015


Height is the distance from the top of the participant’s head to the heels of his or her feet (i.e., the vertical length).


Height or stature is used to assess body size and bone length. Recumbent length is used to measure length of infants, and knee height may be used to estimate height when stature cannot be measured in older adults.

Selection Rationale

The National Health and Nutrition Examination Survey 2007-2008 protocols were selected as best practice methodology and are the most widely used protocols to assess height.


English, Spanish


Common Data Elements (CDE)Person Knee Height Value2794243CDE Browser
Logical Observation Identifiers Names and Codes (LOINC)PhenX - knee height protocol62335-5LOINC

Process and Review

The [link[phenx.org/node/62|Expert Review Panel #1]] reviewed the measures in the Anthropometrics, Diabetes, Physical Activity and Physical Fitness, and Nutrition and Dietary Supplements domains.

Guidance from the ERP includes:

• Added replicate measure language

• Changed unit of measurement

Back-compatible: no changes to Data Dictionary

Previous version in Toolkit archive ([link[www.phenxtoolkit.org/index.php?pageLink=browse.archive.protocols&id=20000|link]])


Centers for Disease Control and Prevention, National Center for Health Statistics. (1988). National Health and Nutrition Examination Survey 1988-1994: Body Measurements (Anthropometry). Hyattsville, MD: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention.

A video of anthropometric procedures is available at http://www.cdc.gov/nchs/nhanes/nhanes3/anthropometric_videos.htm.

General References

Chumlea, W. C., Guo, S. S., Wholihan, K., Cockram, D., Kuczmarski, R. J., & Johnson, C. L. (1998). Stature prediction equations for elderly non-Hispanic, white, non-Hispanic black, and Mexican American persons developed from NHANES III data. Journal of the American Dietetic Association, 98(2), 137-142.

Himes, J. H. (1989). Reliability of anthropometric methods and replicate measurements. (1989). American Journal of Physical Anthropology, 79, 77-80.

Protocol ID:



Export Variables
Variable NameVariable IDVariable DescriptionVersiondbGaP Mapping
PX020701_Knee_Height_1PX020701010000Knee Height measured in centimeter, first measurement4Variable Mapping
PX020701_Knee_Height_2PX020701020000Knee Height measured in centimeter, second measurement4Variable Mapping
PX020701_Knee_Height_3PX020701030000Knee Height measured in centimeter, third measurement4Variable Mapping
PX020701_Knee_Height_AveragePX020701040000Knee Height measured in centimeter, average4Variable Mapping