Anthropometrics Measurement: Knee Girth Measurement

Knee girth, also called knee circumference, is a tape-based measurement used to record the size of the knee region. It is commonly used when professionals want to monitor knee size, compare sides or track swelling-related change over time.

The knee region includes bone, joint structures, tendons, ligaments, muscle, fat and fluid-sensitive tissues. Because of this, knee girth does not explain why the knee is larger or smaller. It simply records the external circumference at the chosen measurement site.

In Measurz, knee girth can be recorded alongside knee range of motion, thigh girth, calf girth, strength testing, balance, hop testing, pain ratings, gait observations and other lower-limb measures. This makes the result more useful because changes in knee size can be reviewed alongside changes in movement, strength and function.

Knee girth should not be used on its own to diagnose an injury, measure joint integrity, determine tissue healing or make return-to-sport decisions. It is best used as an objective tracking measure that supports a broader assessment.

What Is Knee Girth Measurement?

Knee girth measurement records the circumference around the knee using a flexible measuring tape.

The measurement site must be clearly defined. Common options include:

• Around the knee at the level of the mid-patella
• Around the knee at the widest visible knee circumference
• A set distance above the patella
• A set distance below the patella
• A protocol-specific site used by your organisation

For routine Measurz use, measuring around the knee at the level of the mid-patella is a practical method because the patella provides a clear landmark. However, if your organisation uses another method, that method can be used as long as it is clearly recorded and repeated consistently.

The result is usually recorded in centimetres or millimetres.

Why It Is Used

Knee girth measurement may be used to:

• Record baseline knee size
• Compare right and left knee circumference
• Monitor swelling-related change
• Track change over repeated sessions
• Add context to knee range of motion
• Add context to thigh and calf girth
• Add context to strength testing
• Add context to balance, hop or jump testing
• Monitor response to workload or activity
• Support lower-limb assessment records
• Provide objective information for Measurz progress reports

Knee girth is most useful when it is repeated over time using the same method. A single measurement is less useful than a clear trend.

What It Measures

Knee girth measures the external circumference of the knee at the selected measurement site.

It may provide useful information about:

• Knee region size
• Side-to-side difference
• Change from baseline
• Possible swelling or fluid-related change
• Response to recent activity
• Context for knee range of motion
• Context for lower-limb strength and function

It does not directly measure:

• Ligament integrity
• Meniscus status
• Cartilage health
• Tendon health
• Muscle strength
• Balance
• Functional capacity
• Pain source
• Injury diagnosis
• Tissue healing
• Readiness for sport or work

Knee girth is a supporting measure within a broader knee and lower-limb assessment.

Equipment Required

To measure knee girth in Measurz, you will need:

• Flexible non-elastic measuring tape
• Measurz app
• Selected knee girth assessment or body measurement field
• Clear knee landmark
• Optional skin-safe marker
• Plinth, chair or standing setup depending on your chosen protocol
• Notes field for side, position, landmark and conditions

A non-elastic tape is recommended because stretchy tapes can change length and reduce repeatability.

How to Measure Knee Girth

1. Prepare the client

Explain the purpose of the measurement clearly.

A useful explanation is:

“We are going to measure the circumference of your knee so we can record a baseline and compare it over time. This can help us track size changes, but it does not diagnose the reason for those changes by itself.”

Ask the client to remove bulky clothing from around the knee where appropriate. The tape should be placed directly on the skin or over very light clothing depending on the setting and privacy requirements.

Before testing, record:

• Side tested
• Measurement site
• Client position
• Knee position
• Current symptoms
• Visible swelling
• Recent activity
• Time of day if relevant
• Any reason the result may not compare directly with previous sessions

2. Choose the measurement site

Choose one knee measurement site and repeat it every time.

A practical method is:

1. Locate the patella.
2. Identify the midpoint of the patella.
3. Place the tape around the knee at the level of the mid-patella.
4. Keep the tape level and consistent.

If you choose a different site, such as a set distance above or below the patella, record the exact distance and repeat that same method at retest.

3. Position the client

Use the same client position each time.

Common positions include:

• Supine with the knee relaxed
• Long sitting with the leg supported
• Sitting with the knee flexed to a chosen angle
• Standing with weight evenly distributed

For many assessment settings, supine or long sitting can be useful because the limb is supported and the knee can remain relaxed. If standing is used, record it clearly because weight-bearing may affect tissue position.

The same knee angle should be used each time. Do not compare a relaxed extended-knee measurement with a flexed-knee measurement unless your protocol specifically requires it.

4. Apply the measuring tape

Wrap the tape around the knee at the chosen landmark.

Check that the tape is:

• Flat against the skin
• Level around the knee
• Not twisted
• Firm but not compressive
• Not hanging loosely
• Positioned at the same landmark around the entire knee

Avoid pressing the tape into the tissue. Excessive tape tension can reduce the measurement.

5. Record the measurement

Read the measurement carefully and record the value in centimetres or millimetres.

If measuring both knees, repeat the same method on the opposite side.

6. Repeat the measurement if required

For improved confidence, take two measurements on each side.

If the two values differ more than expected, recheck the landmark, tape level and knee position, then take a third measurement.

A practical approach is to record the average of two close values.

7. Save the result in Measurz

Enter the result into Measurz and include relevant notes.

Useful notes include:

• Right or left knee
• Knee girth value
• Measurement site
• Mid-patella, above-patella or below-patella method
• Knee position
• Client position
• Measurement unit
• Number of trials
• Visible swelling
• Symptoms
• Recent activity
• Any change from the usual protocol

Scoring and Interpretation

The main score is knee girth, usually recorded in centimetres.

A higher value means the measured knee circumference is larger. A lower value means the measured knee circumference is smaller.

Interpretation should consider:

• Same-side change over time
• Right-left comparison
• Measurement site
• Knee position
• Client position
• Tape tension
• Visible swelling
• Recent exercise or loading
• Symptoms
• Range of motion results
• Thigh and calf girth
• Strength testing
• Balance, hop or jump testing
• Gait or movement findings

An increase in knee girth may reflect swelling, fluid change, tissue size change, activity response or measurement variation. A decrease may reflect reduced swelling, body composition change, reduced tissue size or measurement variation.

Knee girth should be interpreted with other Measurz assessment data rather than on its own.

Normative Data, Benchmarks or Reference Values

Peer-reviewed universal knee girth norms are limited. Knee girth is usually more useful as a tracking measure than a population score. It can help monitor swelling, post-injury changes, side-to-side differences and response to loading. In Measurz, knee girth should be measured at the same landmark and knee position each time, then compared with the other side, the person’s baseline, symptoms, range of motion, strength and function.

Reliability and Validity

Knee girth can be reliable when the same method is used each time.

Reliability improves when:

• The same measuring tape is used
• The same landmark is used
• The same knee position is used
• The same client position is used
• The same tape tension is used
• The same side is measured
• The same number of trials is taken
• Recent activity and symptoms are recorded
• Notes are entered clearly in Measurz

Knee girth is valid as a circumference measurement when performed correctly. It can provide practical information about knee size and swelling-related change, but it does not directly measure joint damage, ligament status, strength, pain source or functional capacity.

Common Errors and Limitations

Common errors include:

• Measuring at a different knee height each time
• Not recording the landmark used
• Measuring at mid-patella one session and above the patella the next
• Changing knee angle between sessions
• Pulling the tape too tightly
• Leaving the tape too loose
• Measuring over bulky clothing
• Not recording side
• Not recording recent activity
• Treating knee girth as a diagnosis

Limitations include:

• It does not explain the cause of swelling
• It does not measure strength
• It does not measure range of motion
• It does not assess ligament or meniscus status
• It can be affected by activity and time of day
• Small changes may reflect measurement error
• Different landmarks produce different values
• A single score should not be overinterpreted

Practical Applications

Knee girth measurement may be useful for:

• Baseline knee assessment
• Monitoring knee size over time
• Comparing right and left knees
• Tracking swelling-related changes
• Adding context to range of motion
• Adding context to quadriceps and hamstring testing
• Adding context to hop and jump testing
• Supporting lower-limb progress reports
• Client education
• Measurz body measurement records

For example, if knee girth decreases while knee range of motion, strength and hop confidence improve, the overall assessment trend may be more positive. If knee girth increases after a workload spike, it may provide useful context for interpreting symptoms and deciding what to reassess.

How to Record This in Measurz

When recording knee girth in Measurz, include:

• Client name
• Test date
• Right or left knee
• Knee girth value
• Measurement unit
• Measurement site
• Knee position
• Client position
• Number of trials
• Visible swelling if present
• Symptoms if relevant
• Recent activity or workload
• Any reason the test was modified

For best results, use the same landmark, same knee position and same tape tension every time.

Measurz can help organise knee girth alongside knee range of motion, thigh girth, calf girth, strength testing, balance, hop testing and other lower-limb results.

FAQs

What is knee girth?

Knee girth is the circumference around the knee measured with a flexible tape.

Where should I measure knee girth?

A practical method is to measure around the knee at the level of the mid-patella. Other methods can be used, but the landmark must be recorded and repeated.

Should I measure both knees?

Yes, if side-to-side comparison is relevant.

Does knee girth measure swelling?

Knee girth can help track knee size changes that may relate to swelling, but it does not explain the cause.

Does knee girth diagnose a knee injury?

No. Knee girth is not a diagnostic test.

Can knee girth change after exercise?

Yes. Activity, loading, fluid change and swelling can affect the measurement.

Are there universal knee girth norms?

No. Knee girth should usually be compared with the client’s own baseline or opposite side.

Should knee girth be used alone?

No. It should be interpreted alongside other Measurz assessment findings.

Key Takeaways

Knee girth measures knee circumference.

The measurement landmark must be clearly recorded and repeated.

There are no widely accepted universal knee girth norms.

Knee girth is useful for tracking size change and comparing sides.

Knee girth does not diagnose injury or directly measure strength, range of motion or readiness.

It should be interpreted alongside other Measurz assessment findings.

References

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.

Nicholas, J. J., Taylor, F. H., Buckingham, R. B., & Ottonello, D. (1976). Measurement of circumference of the knee with ordinary tape measure. Annals of the Rheumatic Diseases, 35(3), 282–284.

Suchy, J. P., Glasoe, W. M., & Koehler, L. A. (2023). A tissue dielectric constant evaluation of knee edema: A retrospective intra-rater reliability and association study of repeated measures. Cureus, 15(7), e42089. https://doi.org/10.7759/cureus.42089 

Pua, Y. H. (2015). The time course of knee swelling post total knee arthroplasty and its associations with quadriceps strength and gait speed. Journal of Arthroplasty, 30(7), 1215–1219. https://doi.org/10.1016/j.arth.2015.02.010

Bazzucchi, I., Riccio, M. E., & Felici, F. (2020). Are body circumferences able to predict strength, muscle mass and bone characteristics? Journal of Functional Morphology and Kinesiology, 5(3), 52. https://doi.org/10.3390/jfmk5030052