Leg length measurement records the length of the lower limb using a defined anatomical method. It is commonly used in health, fitness, sport, workplace, rehabilitation and performance settings to support lower-limb profiling, side-to-side comparison and assessment planning.
A common clinical tape method for true leg length measures from the anterior superior iliac spine, known as the ASIS, to the medial malleolus at the ankle. This provides a practical estimate of limb length using bony landmarks.
Leg length can provide useful context for movement, gait, posture, running, jumping, lower-limb strength testing and equipment setup. It may also help identify whether a side-to-side length difference should be considered when interpreting assessment data.
However, tape-based leg length measurement has limitations. It can be affected by landmark accuracy, pelvic position, limb girth, joint position and body shape. If precise leg length discrepancy measurement is required, imaging methods are generally more accurate than tape measurement.
In Measurz, leg length should be recorded as a practical assessment value and interpreted alongside other findings, such as gait, strength, range of motion, balance, hop testing, symptoms and function.
Leg length measurement is a method of estimating the length of the lower limb.
A common direct method is true leg length, measured from:
Anterior superior iliac spine (ASIS) to medial malleolus
The ASIS is the bony point at the front of the pelvis. The medial malleolus is the bony point on the inside of the ankle.
The result is usually recorded in centimetres.
Another method is apparent leg length, often measured from the umbilicus to the medial malleolus. This may reflect pelvic position and apparent asymmetry rather than true bony limb length.
For most Measurz workflows, true leg length using ASIS to medial malleolus is the preferred practical method when using a tape measure.
Leg length measurement may be used to:
Record lower-limb length
Compare left and right sides
Add context to gait observations
Add context to running or walking assessment
Add context to hop and jump testing
Add context to lower-limb strength testing
Support bike, equipment or setup considerations
Support body measurement profiling
Track lower-limb development in younger clients where appropriate
Help decide whether further assessment may be required
Leg length is most useful when interpreted with movement and performance data. A small side-to-side difference may not matter for one person but may be relevant in another depending on symptoms, sport, work demands and movement patterns.
True leg length measures the distance from the ASIS to the medial malleolus.
It may provide useful information about:
Lower-limb length
Side-to-side length difference
Body measurement profile
Lower-limb proportion
Context for gait and movement assessment
Context for equipment setup
Context for lower-limb performance testing
It does not directly measure:
Strength
Power
Balance
Mobility
Pain source
Injury diagnosis
Joint health
Running technique
Functional capacity
Readiness for sport or work
Leg length is a supporting measurement within a wider lower-limb assessment.
To measure leg length in Measurz, you will need:
Flexible non-elastic measuring tape
Measurz app
Plinth or flat testing surface
Clear anatomical landmarks
Optional skin-safe marker
Notes field for side, position and conditions
A non-elastic tape is recommended because stretchy tapes can affect the reading.
Explain the purpose of the measurement clearly.
A useful explanation is:
“We are going to measure the length of each leg from your pelvis to the inside of your ankle. This can help us compare sides and add context to your other lower-limb results.”
Ask the client to remove shoes and bulky clothing that may block landmarks.
Before testing, record:
Side tested
Measurement method
Client position
Any pain, stiffness or positioning limitation
Any reason the result may not compare directly with previous sessions
Ask the client to lie supine on a firm, flat surface.
The client should be positioned with:
Pelvis as level as possible
Legs relaxed
Knees extended where possible
Feet relaxed
Body straight on the plinth
If the client cannot lie straight or extend the knees comfortably, record this in Measurz.
Locate the anterior superior iliac spine on the side being measured.
This is the bony point at the front of the pelvis.
If appropriate, mark the point lightly with a skin-safe marker to improve repeatability.
Locate the medial malleolus on the same side.
This is the bony point on the inside of the ankle.
Place the zero end of the tape at the ASIS.
Run the tape in a straight line to the medial malleolus.
Check that the tape is:
Straight
Not twisted
Not following a curved path around the limb
Applied with light tension
Ending at the same ankle landmark each time
Record the result in centimetres.
Measure the other leg using the same method.
Compare right and left values only if the same landmarks and positioning were used on both sides.
For improved confidence, take two measurements per side.
If the values differ more than expected, recheck the landmarks and repeat.
A practical approach is to record the average of two close values.
Enter the result into Measurz and include notes.
Useful notes include:
Right leg length
Left leg length
ASIS to medial malleolus method
Client position
Number of trials
Any positioning limitation
Any reason the result may not compare directly with previous sessions
The main scores are right leg length and left leg length.
A side-to-side difference may be recorded as the difference between the two values.
Interpretation should consider:
Measurement error
Landmark accuracy
Pelvic position
Knee position
Foot and ankle position
Client body shape
Lower-limb girth differences
Gait observations
Strength and range of motion results
Balance and hop testing
Symptoms and function
Sport or work demands
A small side-to-side difference is common and may not be meaningful. Larger differences may need more careful interpretation, especially if they are associated with symptoms, gait changes or performance differences.
Tape measurement should not be treated as a precise diagnosis of leg length discrepancy. If accurate leg length discrepancy measurement is important, further assessment or imaging may be required.
Leg length has reference data in research, but the meaning depends on the exact protocol. “Leg length” may mean anatomical leg length, functional leg length, upper-leg length, lower-leg length or another segment measure. Because of this, there is no single universal value that applies to all testing methods. Leg length is often used to understand body proportion, gait, sport demands and possible side-to-side differences. In Measurz, the most important step is to record the exact landmarks and compare the same method over time.
Tape-based leg length measurement can be useful, but it has limitations.
Reliability improves when:
The same landmarks are used
The same body position is used
The pelvis is positioned consistently
The knees are positioned consistently
The same tape is used
The same professional performs the measurement
Multiple trials are taken
Notes are recorded clearly in Measurz
Tape measurement is practical and accessible, but it can be affected by difficulty finding landmarks, soft tissue, limb shape and joint position. Imaging methods are generally more accurate when precise leg length discrepancy measurement is required.
Common errors include:
Measuring from the wrong pelvic landmark
Measuring to the wrong ankle landmark
Letting the tape curve around the leg
Using different landmarks between sides
Not positioning the pelvis consistently
Measuring with knees bent on one side
Measuring over bulky clothing
Pulling the tape too tightly
Not repeating the measurement
Treating tape measurement as perfectly precise
Limitations include:
Landmarking can be difficult
Pelvic position can affect the result
Limb girth can affect tape path
Joint position can affect measurement
Small differences may reflect measurement error
Tape methods are less accurate than imaging
Leg length alone does not explain pain or movement patterns
Leg length measurement may be useful for:
Lower-limb profiling
Side-to-side comparison
Gait assessment context
Running assessment context
Hop and jump testing context
Lower-limb strength testing context
Bike or equipment setup considerations
Growth and development tracking where appropriate
Measurz body measurement reports
For example, if one leg measures shorter and the client also shows gait asymmetry, different hop performance or repeated loading issues, leg length may be one piece of the broader assessment. It should not be used alone to explain the findings.
When recording leg length in Measurz, include:
Client name
Test date
Right leg length
Left leg length
Measurement unit
ASIS to medial malleolus method
Client position
Number of trials
Any positioning limitation
Any pain or stiffness affecting setup
Any reason the result may not compare directly with previous sessions
For best results, use the same method, same landmarks and same body position every time.
Measurz can help organise leg length alongside arm length, height, gait, range of motion, strength, balance, hop testing and other lower-limb results.
True leg length is commonly measured from the ASIS at the front of the pelvis to the medial malleolus at the inside of the ankle.
Apparent leg length is often measured from the umbilicus to the medial malleolus. It may reflect pelvic position or apparent asymmetry rather than true limb length.
Yes. Measuring both sides allows side-to-side comparison.
No. Tape measurement is practical but can be affected by landmarking, body shape and position.
Imaging-based methods are generally more accurate when precise measurement is required.
Not by itself. Leg length may provide context, but it should be interpreted with other assessment findings.
Centimetres are usually most practical for Measurz recording.
Yes. Shoes should be removed for accurate landmarking and positioning.
Leg length measurement records lower-limb length.
The common true leg length tape method measures from ASIS to medial malleolus.
Both sides should be measured if side-to-side comparison is needed.
Tape measurement is practical but not perfectly precise.
There are no simple universal leg length norms.
Leg length should be interpreted alongside gait, strength, range of motion, balance, hop testing and other Measurz findings.
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