Knee height is an anthropometric measurement used to record the distance from the heel or foot support surface to the front of the thigh near the knee when the knee and ankle are positioned at approximately 90 degrees. It is commonly used in body measurement and height-estimation contexts.
Knee height can be particularly useful when standing height is difficult or not appropriate to measure. For example, some clients may not be able to stand fully upright, may have posture limitations or may require an alternative body measurement approach. Knee height can provide useful profile information and may be used in validated equations to estimate stature.
In Measurz, knee height can be recorded as part of a broader body measurement profile. It may be reviewed alongside standing height, leg length, arm span, weight, BMI, lower-limb measurements and other assessment results.
Knee height should not be interpreted as a performance measure. It does not measure strength, mobility, balance or function by itself. It is a body measurement that provides context.
Knee height measurement records the vertical distance from the heel or foot support to the anterior surface of the thigh near the knee, with the knee and ankle positioned at approximately 90 degrees.
It is commonly measured using a sliding broad-blade caliper or knee-height caliper. In some settings, a tape or other measuring tool may be used, but a proper anthropometry caliper is preferred for repeatability.
The result is usually recorded in centimetres.
Knee height is often used as an alternative measure for estimating standing height. This can be useful when standing height is hard to measure accurately.
Knee height measurement may be used to:
Record lower-limb segment profile
Estimate standing height when height cannot be measured directly
Support body measurement profiling
Add context to leg length and lower-limb measurements
Support BMI calculation when direct height is unavailable
Support anthropometry assessment in people who cannot stand fully upright
Monitor growth and body proportions where appropriate
Add context to Measurz body measurement records
Knee height is most useful when there is a clear reason to measure it, such as estimating stature or recording lower-limb proportions.
Knee height measures a lower-limb segment related to body proportions and stature.
It may provide useful information about:
Lower-limb segment size
Body measurement profile
Stature estimation context
Growth or development context where appropriate
Relationship to standing height
Relationship to leg length and body proportions
It does not directly measure:
Strength
Power
Balance
Mobility
Knee range of motion
Pain source
Injury diagnosis
Functional capacity
Readiness for sport or work
Movement quality
Knee height is best interpreted as an anthropometric measurement, not a functional test.
To measure knee height in Measurz, you will need:
Knee-height caliper or sliding anthropometry caliper
Firm chair, plinth or measurement setup
Measurz app
Consistent client position
Clear measurement method
Notes field for side, position and equipment used
A knee-height caliper is preferred because it provides a more standardised measurement than a flexible tape.
Explain the purpose of the measurement clearly.
A useful explanation is:
“We are going to measure your knee height. This is a body measurement that can help record your lower-limb profile and may be used to estimate standing height if needed.”
Ask the client to remove shoes if required by your protocol.
Before testing, record:
Side tested
Measurement equipment
Client position
Whether shoes were removed
Any knee, hip or ankle positioning limitation
Any reason the result may not compare directly with previous sessions
Position the client so the knee and ankle are approximately at 90 degrees.
This can be done in sitting or lying depending on the equipment and protocol.
A practical seated setup includes:
Client sitting upright
Hip and knee flexed to approximately 90 degrees
Foot flat or positioned on the caliper footplate
Ankle at approximately 90 degrees
Lower leg vertical
Thigh supported and relaxed
The same side and same position should be used at retest.
Place the fixed blade of the knee-height caliper under the heel or foot support, depending on the device.
Place the moving blade over the anterior surface of the thigh just above the knee, according to the device and protocol.
The caliper should be aligned with the lower leg and applied gently but firmly.
Before taking the reading, check that:
The knee is close to 90 degrees
The ankle is close to 90 degrees
The lower leg is vertical
The foot is positioned consistently
The caliper is aligned correctly
The client is relaxed
The measurement blades are in the correct position
Poor positioning can affect the result.
Read the value in centimetres.
Record the result carefully in Measurz.
If the device records in millimetres, convert or enter the value according to your Measurz setup.
For improved confidence, take a second measurement.
If the results are not close, check the setup and repeat.
A practical approach is to record the average of two close measurements.
Enter the result into Measurz with relevant notes.
Useful notes include:
Right or left side
Knee height value
Measurement unit
Sitting or lying position
Knee-height caliper used
Shoes removed or not
Number of trials
Any positioning limitation
Any reason the result may not compare directly with previous sessions
The main score is knee height, usually recorded in centimetres.
Interpretation should consider:
Side measured
Client position
Equipment used
Knee and ankle position
Whether shoes were removed
Relationship to standing height
Whether the value is being used for height estimation
Age, sex and population context if using an equation
Any positioning limitation
Knee height can be used in equations to estimate standing height, but the equation must be appropriate for the person being assessed. Different equations have been developed for different populations, age groups and settings.
Knee height should not be used as a performance score. It is a body measurement used for profiling or height estimation.
There are no simple “good” or “bad” knee height norms.
Knee height mainly reflects body size and lower-limb proportions.
For most Measurz users, the most useful uses are:
Recording the client’s own knee height
Comparing it with standing height or leg length if relevant
Using it to estimate height when standing height cannot be measured
Tracking growth in younger clients where appropriate
If knee height is used to estimate height, use an equation that matches the client as closely as possible. Do not treat knee height as a pass/fail score.
Knee height can be reliable when measured with a standardised method and appropriate equipment.
Reliability improves when:
A knee-height caliper is used
The same side is measured
The same position is used
The knee and ankle are positioned at approximately 90 degrees
The same equipment is used
The same number of trials is taken
The client is relaxed
Notes are recorded clearly in Measurz
Knee height is valid as an anthropometric lower-limb segment measurement when performed correctly. It can also support stature estimation when appropriate equations are used, but it is not a perfect substitute for measured standing height in every person.
Common errors include:
Measuring with the knee at the wrong angle
Measuring with the ankle at the wrong angle
Using a tape measure when a caliper is needed
Measuring the wrong side without recording it
Not removing shoes when the protocol requires it
Poor caliper alignment
Pressing the caliper too firmly
Not repeating the measurement
Using an equation that does not match the client population
Treating estimated height as the same as directly measured height
Limitations include:
Knee height does not measure strength or function
It requires correct positioning
It is less useful if the knee or ankle cannot be positioned correctly
Height-estimation equations are population-specific
It should not replace measured standing height when accurate standing height is available
A single value should not be overinterpreted
Knee height may be useful for:
Body measurement profiling
Estimating height when standing height is difficult
Supporting BMI calculation when direct height is unavailable
Recording lower-limb proportions
Growth and development tracking where appropriate
Anthropometry assessment
Measurz body measurement reports
For example, if a client cannot stand fully upright, knee height may provide a practical alternative way to estimate height for BMI or body profile purposes. The estimated height should be clearly labelled as estimated rather than directly measured.
When recording knee height in Measurz, include:
Client name
Test date
Right or left side
Knee height value
Measurement unit
Equipment used
Sitting or lying position
Whether shoes were removed
Number of trials
Any hip, knee or ankle positioning limitation
Whether the result was used to estimate height
Any equation used, if applicable
For best results, measure knee height with the same equipment and position each time.
Measurz can help organise knee height alongside standing height, weight, BMI, leg length, arm span and other body measurements.
Knee height is an anthropometric measurement taken with the knee and ankle positioned at about 90 degrees.
It can help record lower-limb body proportions and may be used to estimate standing height when height cannot be measured directly.
A knee-height caliper or sliding anthropometry caliper is preferred.
Yes, if your protocol requires it. Record whether shoes were removed.
Yes, but only when an appropriate equation is used. It should be labelled as an estimate.
No. Knee height is a body measurement, not a performance test.
No. Knee height mainly reflects body size and body proportions.
Use measured standing height where possible. Knee height is useful when standing height cannot be measured accurately.
Knee height measures a lower-limb segment with the knee and ankle positioned at about 90 degrees.
It is commonly used to help estimate height when standing height is difficult to measure.
There are no simple “good” or “bad” knee height norms.
A knee-height caliper is preferred for consistency.
Knee height does not measure strength, mobility, pain or performance.
It should be recorded clearly in Measurz and interpreted as part of a broader body measurement profile.
Centers for Disease Control and Prevention, National Center for Health Statistics. (2021). National Health and Nutrition Examination Survey: 2021 anthropometry procedures manual. Centers for Disease Control and Prevention.
Chumlea, W. C., Roche, A. F., & Steinbaugh, M. L. (1985). Estimating stature from knee height for persons 60 to 90 years of age. Journal of the American Geriatrics Society, 33(2), 116–120. https://doi.org/10.1111/j.1532-5415.1985.tb02276.x
Lohman, T. G., Roche, A. F., & Martorell, R. (Eds.). (1988). Anthropometric standardization reference manual. Human Kinetics.
Marfell-Jones, M., Stewart, A., & de Ridder, H. (2012). International standards for anthropometric assessment. International Society for the Advancement of Kinanthropometry.
PhenX Toolkit. (n.d.). Knee height protocol. RTI International.
