Range of Motion: 90/90 Active Knee Extension (AKE)

The 90/90 Active Knee Extension Test measures how far the client can actively straighten the knee while the hip is held at approximately 90 degrees. It is commonly used to assess posterior thigh mobility and side-to-side differences.

Introduction

The 90/90 Active Knee Extension Test, often shortened to AKE, is a practical way to assess knee extension range while the hip is flexed. This position places the hamstrings under length and helps professionals compare posterior thigh mobility between sides.

The result should be interpreted as a movement and flexibility measure, not as a stand-alone explanation for pain, injury risk or performance.

Quick Summary

• Client lies supine with hip and knee at 90 degrees.
• Client actively straightens the knee as far as comfortable.
• Score is usually recorded as knee extension angle or extension deficit.
• Pelvic and hip position must be controlled.
• Compare sides and track baseline change.

What Is the 90/90 Active Knee Extension Test?

The AKE test measures active knee extension with the hip flexed to approximately 90 degrees. It provides information about posterior thigh mobility, active control and symptom response in a standardised hip-flexed position.

Why It Is Used

It is used to:

• assess posterior thigh mobility
• compare left and right sides
• monitor flexibility changes
• guide exercise programming
• track response to mobility or loading interventions
• support return-to-running or kicking context alongside other tests

What It Measures

The test measures active knee extension range in a hip-flexed position. It may be influenced by:

• hamstring length and tolerance
• neural sensitivity
• pelvic control
• hip flexion angle
• pain or apprehension
• active quadriceps effort
• warm-up and fatigue
• device placement

Who It Is Useful For

Useful for:

• runners
• field and court athletes
• dancers and kickers
• general fitness clients
• clients with posterior thigh mobility goals
• professionals tracking flexibility alongside strength and function

Equipment Required

• Firm plinth or mat
• Inclinometer or goniometer
• Optional strap, box or examiner support to maintain hip at 90 degrees
• Pain scale
• Measurz profile

Step-by-Step Protocol / Practice

1. Client position. Lie supine.
2. Hip position. Flex the test hip to 90 degrees. The opposite leg stays relaxed and extended unless another standardised variation is chosen.
3. Knee starting position. Begin with the test knee flexed to 90 degrees.
4. Stabilise. Maintain the thigh vertical and avoid pelvic rotation or posterior pelvic tilt.
5. Instruction. Ask: “Slowly straighten your knee as far as comfortable while keeping your thigh still.”
6. End point. Stop at the client’s active limit, symptom limit or loss of hip/pelvic position.
7. Measure. Record the final knee angle using a goniometer or inclinometer.
8. Symptoms. Record posterior thigh stretch, pain, neural symptoms or apprehension.
9. Trials. Use one familiarisation trial and one to three recorded trials.
10. Retest. Use the same hip angle, instructions, device and scoring convention.

Scoring and Interpretation

The score can be recorded as:

• final knee extension angle
• degrees lacking from full knee extension
• side-to-side difference

A smaller extension deficit generally reflects greater active knee extension range in the test position. A larger deficit suggests less available range or reduced active tolerance in that position.

Interpret alongside:

• symptoms
• pelvic control
• active versus passive findings if available
• straight leg raise or hip flexion results
• running, kicking or hinge movement goals
• strength and function measures

Normative Data, Benchmarks or Reference Values

Evidence level: Level 2 — related or closest available benchmarks.

Exact norms vary by population and protocol. A 2024 study investigated AKE cut-off approaches for hamstring tightness using a supine 90-degree hip and knee position with goniometric measurement, but such cut-offs should be used cautiously and not treated as universal pass/fail criteria.  

Older and sport-specific studies provide additional context, including values in elite track and field athletes, but protocol and population differences limit direct comparison.  

Use practical comparison:

• baseline AKE score
• left versus right difference
• symptom response
• repeated testing
• sport or task needs
• change beyond known measurement error when available

Reliability and Validity

A 2020 study reported reliability and minimal detectable change for the Ely and AKE tests in asymptomatic adults, supporting the AKE as a trackable measure when protocol is controlled.  

Earlier reliability work also supports AKE measurement when the hip is stabilised, but measurement quality depends on pelvic control, hip angle, device alignment and consistent instructions.  

Do not over-interpret small changes unless they exceed relevant MDC or are repeated consistently.

Sensitivity and Specificity

Sensitivity and specificity are not usually applicable when the AKE test is used as a ROM and flexibility measure. Some studies explore cut-off values for hamstring tightness, but these should not be used as stand-alone diagnostic criteria.

Common Errors and Limitations

• hip not maintained at 90 degrees
• pelvis rotating or tilting
• opposite leg lifting
• measuring passive instead of active range
• unclear scoring convention
• pushing into symptoms
• comparing different protocols
• ignoring neural symptom response

Practical Applications

The AKE test can help with:

• posterior thigh mobility tracking
• running and kicking preparation context
• side-to-side comparison
• monitoring response to mobility work
• identifying whether additional neural, hip or strength testing may add useful context
• progress reporting in Measurz

How to Record This in Measurz

Record:

• test name: 90/90 Active Knee Extension
• side
• active ROM
• score in degrees
• scoring convention
• hip position
• device used
• pain score
• symptom location
• posterior thigh stretch response
• pelvic compensation
• comparison side
• baseline
• retest date
• related hip flexion, straight leg raise or strength findings

Example: “Right 90/90 AKE: 28° extension deficit, active, hip held at 90°, pain 0/10, posterior thigh stretch, pelvis stable. Left: 20° deficit.”

Related Tests / Internal Links

• Knee Flexion Test
• Knee Extension Test
• Spine Straight Leg Raise Test
• Hip Flexion Test
• Knee Prone Heel-to-Butt Test

FAQs

What does the 90/90 Active Knee Extension Test measure?
It measures active knee extension range with the hip held in flexion, often used as posterior thigh mobility context.

Is the AKE test active or passive?
This version is active. Passive knee extension is a related but different test and should be recorded separately.

What is a normal AKE score?
There is no single universal normal. Values vary by age, sport, sex, symptoms and protocol.

What does a side-to-side difference mean?
It shows asymmetry in this test position and should be interpreted with symptoms, strength and functional findings.

Key Takeaways

• Control hip and pelvis position.
• Record the scoring convention clearly.
• Compare sides and baseline.
• Use AKE as movement information, not a stand-alone explanation.

References

Olivencia, O., Godinez, G. M., Dages, J., Duda, C., Kaplan, K., Kolber, M. J., Kaplan, P. T., & Kolber, M. J. (2020). The reliability and minimal detectable change of the Ely and Active Knee Extension tests. International Journal of Sports Physical Therapy, 15(5), 776–782. https://doi.org/10.26603/ijspt20200776

Hori, M., et al. (2024). Optimal cut-off values of the active knee extension test for assessing hamstring tightness. Journal of Bodywork and Movement Therapies.