The Slocum Test is a modified anterior drawer-style test used to assess anterolateral or anteromedial rotatory knee instability by changing tibial rotation. A positive result may suggest rotational laxity or increased anterior translation compared with the other side, but it does not confirm a specific ligament injury on its own.

Introduction

Rotatory knee instability can involve several structures, including the cruciate ligaments, collateral ligaments, capsule, menisci, anterolateral structures, posteromedial structures and bony alignment.

The Slocum Test attempts to add rotational bias to anterior drawer-style testing. By changing the position of tibial rotation, the examiner may explore different patterns of anterior and rotational knee laxity.

It is commonly used alongside:

• Lachman Test
• Anterior Drawer Test
• Pivot Shift Test
• valgus stress testing
• varus stress testing
• meniscal assessment
• knee swelling assessment
• functional instability testing
• imaging where clinically appropriate

Clinical descriptions identify the Slocum Test as a modification of the Anterior Drawer Test used to assess anteromedial rotary instability and anterolateral rotary instability.  

Quick Summary

• Test name: Slocum Test
• Also known as: Slocum’s test, Slocum rotary instability test
• Body region: Knee
• Purpose: Assess anteromedial or anterolateral rotatory knee instability
• Commonly associated presentation: ACL-related laxity with possible capsular, collateral or rotational involvement
• Positive finding: Increased anterior translation or rotational asymmetry compared with the other side
• Negative finding: No meaningful side-to-side difference in anterior translation or rotational laxity
• Best used with: Lachman Test, Anterior Drawer Test, Pivot Shift Test, varus/valgus stress tests and functional assessment
• Key limitation: Published diagnostic accuracy values for the exact Slocum Test appear limited

What Is the Slocum Test?

The Slocum Test is a modified anterior drawer test.

It assesses anterior tibial translation while the tibia is rotated to bias different rotatory instability patterns.

The test may be used to assess:

• anterolateral rotary instability
• anteromedial rotary instability
• anterior tibial translation with rotational bias
• side-to-side difference
• endpoint quality
• instability response

In clinical descriptions:

• internal tibial rotation is commonly used to assess anterolateral rotary instability
• external tibial rotation is commonly used to assess anteromedial rotary instability

The test is not a stand-alone diagnostic tool.

Why It Is Used

The Slocum Test may help support assessment reasoning when rotational knee instability is suspected.

It may help professionals:

• assess anterior translation with tibial rotation
• compare involved and uninvolved knees
• explore anterolateral versus anteromedial laxity patterns
• identify whether rotational positioning changes instability response
• document side-to-side differences
• guide further ligament or functional testing
• support referral or imaging discussion where appropriate

It should be used as part of a broader knee assessment rather than as a single decision-making test.

What It Assesses

The Slocum Test assesses anterior tibial movement with rotational bias.

It may provide information about:

• anterior tibial translation
• rotational laxity
• anterolateral rotary instability
• anteromedial rotary instability
• endpoint quality
• side-to-side difference
• client apprehension or guarding

It does not directly identify:

• exact ligament torn
• ACL fibre continuity
• partial versus complete ligament injury
• meniscal pathology
• cartilage injury
• bony injury
• return-to-sport readiness

Who It Is Useful For

This test may be useful for:

• experienced rehabilitation professionals
• exercise professionals working within scope
• strength and conditioning professionals working with allied health teams
• movement assessment professionals
• students learning knee special tests
• professionals using Measurz or MAT for structured assessment recording

It may be relevant for clients who report:

• knee giving way
• pivoting injury
• rotational instability
• instability during cutting
• instability during landing
• recurrent knee shift
• previous ACL injury
• possible combined ligament injury

When to Use This Test

Use the Slocum Test when the history suggests possible rotational knee instability and the client can tolerate controlled drawer-style testing.

It may be useful when the client reports:

• giving way
• twisting or pivoting injury
• instability with direction change
• instability during sport
• instability during uneven-ground movement
• previous ACL injury or reconstruction
• symptoms that suggest more than simple pain provocation

The test is more meaningful when it shows clear side-to-side differences in translation, rotation or endpoint quality.

When Not to Use or When to Be Cautious

Use caution with:

• acute traumatic knee injury
• large effusion or suspected haemarthrosis
• suspected fracture
• suspected multi-ligament injury
• severe pain
• high irritability
• recent knee surgery
• marked guarding
• limited knee flexion
• inability to relax the hamstrings

Stop testing if:

• pain escalates
• the client feels unsafe
• guarding prevents accurate testing
• symptoms feel unstable or threatening
• the client asks to stop
• there are red flags requiring medical review

Equipment Required

• Treatment table or plinth
• Pain scale
• Symptom and confidence recording
• Measurz recording workflow
• Optional comparison-side notes
• Optional referral or further assessment notes where appropriate

Step-by-Step Protocol / Practice

Setup

Position the client lying supine.

Explain that the test assesses knee movement with the shin rotated in different positions.

The client should understand that the test will be controlled and stopped if symptoms become unsafe or uncomfortable.

Client Position

• Client lies on their back
• Hip is flexed
• Knee is flexed to approximately 90 degrees
• Foot is placed on the table
• Hamstrings should be relaxed
• Compare both sides where appropriate

Examiner / Professional Position

• Sit lightly on or stabilise the client’s foot
• Face the tested knee
• Place both hands around the proximal tibia
• Keep thumbs near the joint line or tibial tuberosity for reference
• Observe the tibial position before applying force

Hand Placement

• Both hands hold the proximal tibia
• Fingers wrap around the upper calf
• Thumbs rest near the anterior tibia
• Contact should be firm but not painful

Stabilisation

Stabilise the foot and maintain the selected tibial rotation.

Monitor for:

• hamstring contraction
• quadriceps guarding
• hip rotation
• pelvis movement
• foot movement
• pain or apprehension

Testing is less reliable if the client cannot relax.

Movement or Force Direction

Perform anterior tibial translation with the tibia rotated.

Common variations include:

• Internal tibial rotation: used to bias anterolateral rotary instability assessment
• External tibial rotation: used to bias anteromedial rotary instability assessment

Apply a controlled anterior force to the proximal tibia.

Assess:

• amount of anterior translation
• rotational movement
• endpoint quality
• side-to-side difference
• pain or apprehension
• symptom familiarity

Instructions

Ask the client to:

• relax the thigh muscles
• keep the foot relaxed
• report pain, instability or apprehension
• say whether the feeling is familiar
• tell you immediately if they want the test stopped

Example instruction:

“I’m going to hold your shin in a rotated position and gently pull it forward to assess knee stability. Stay relaxed and tell me if you feel pain, instability or a familiar giving-way sensation.”

Positive Finding

A positive Slocum Test may include:

• increased anterior translation compared with the other side
• increased rotational movement
• soft or absent endpoint
• clear asymmetry between internal and external rotation positions
• familiar instability or giving-way sensation
• apprehension linked to instability rather than pain alone

Negative Finding

A negative finding involves:

• firm endpoint
• no meaningful side-to-side translation difference
• no clear rotational asymmetry
• no familiar instability response
• no meaningful difference between rotation positions

Stopping Criteria

Stop if:

• pain increases sharply
• guarding prevents movement
• the client becomes highly apprehensive
• the knee cannot be positioned safely
• symptoms feel unsafe
• the client asks to stop

Safety Notes

• Use controlled force only
• Avoid aggressive pulling
• Do not force tibial rotation
• Compare sides where appropriate
• Record whether laxity, pain or instability was the main finding

Positive and Negative Test Interpretation

A positive Slocum Test may increase suspicion of rotational knee instability when anterior translation or rotational movement is greater than the comparison side.

A positive result is more meaningful when it matches:

• pivoting injury mechanism
• giving-way episodes
• positive Lachman Test
• positive Anterior Drawer Test
• positive Pivot Shift Test
• collateral ligament findings
• meniscal or capsular findings
• functional instability during sport or daily tasks

A positive result does not confirm ACL injury or a specific capsuloligamentous injury on its own.

Other factors may influence the result, including:

• hamstring guarding
• pain
• swelling
• examiner force
• generalised joint laxity
• previous knee injury
• meniscal involvement
• combined ligament injury
• inconsistent tibial rotation
• poor foot stabilisation

A negative Slocum Test may reduce suspicion when:

• the test is performed well
• the client is relaxed
• no side-to-side difference is present
• related ligament tests are also negative
• the history is not strongly suggestive of instability

However, a negative result does not fully exclude ACL injury or rotational instability.

Some clients may only show instability during:

• pivoting
• cutting
• landing
• fatigue
• sport-specific movement
• higher-speed tasks

Interpretation is stronger when combined with history, swelling, Lachman Test, Anterior Drawer Test, Pivot Shift Test, collateral ligament tests, functional assessment and imaging where clinically appropriate.

Sensitivity, Specificity and Diagnostic Accuracy

High-quality diagnostic accuracy evidence reporting sensitivity, specificity or likelihood ratios for the exact Slocum Test appears limited.

At the time of writing:

• Sensitivity: no high-quality published value found for this exact test and population
• Specificity: no high-quality published value found for this exact test and population
• Positive likelihood ratio: not established
• Negative likelihood ratio: not established
• Reference standard: not consistently established for this test

Clinical descriptions present the Slocum Test as a modified Anterior Drawer Test for anteromedial and anterolateral rotary instability, but exact diagnostic values are not well established in the sources found.  

For broader ACL physical examination, recent reviews show that commonly used ACL tests such as Lachman, Anterior Drawer, Pivot Shift and Lever Sign vary in accuracy by setting, timing and study design. These values should not be directly assigned to the Slocum Test.  

Practical interpretation:

• A positive Slocum Test may increase suspicion when it shows clear asymmetry and matches the client’s history.
• A negative Slocum Test does not exclude ACL injury or rotatory instability.
• The test should be interpreted as a rotational drawer-style assessment, not a stand-alone diagnostic procedure.
• Stronger interpretation comes from clusters of findings rather than one test result.

Reliability and Validity

Specific reliability values for the Slocum Test appear limited.

Reliability may be influenced by:

• knee flexion angle
• degree of tibial rotation
• anterior force magnitude
• hand placement
• foot stabilisation
• client relaxation
• hamstring guarding
• pain and swelling
• examiner experience
• whether a binary or graded result is used

Validity is stronger when:

• the test reproduces familiar instability
• clear side-to-side difference is present
• results match Lachman, Anterior Drawer or Pivot Shift findings
• history suggests rotational instability
• functional tasks reproduce similar instability
• imaging findings, where available, support the broader presentation

Validity is weaker when:

• pain is the only response
• the client guards strongly
• swelling limits motion
• tibial rotation is inconsistent
• no comparison side is available
• symptoms occur only during sport-specific tasks

Rotatory knee instability is complex and can involve multiple structures, including cruciate ligaments, collateral structures, capsule, menisci and alignment factors. This supports the need to interpret the Slocum Test as one part of a broader assessment rather than as an isolated finding.  

Common Errors and Limitations

Common errors include:

• not stabilising the foot
• allowing hamstring contraction
• inconsistent tibial rotation
• pulling too aggressively
• not comparing both sides
• interpreting pain alone as a positive test
• failing to assess endpoint quality
• confusing anterior translation with rotational instability
• using the test as a stand-alone ACL diagnosis
• not recording whether internal or external rotation was used

Limitations include:

• limited diagnostic accuracy evidence
• limited published reliability data
• examiner-dependent technique
• difficulty standardising tibial rotation
• reduced usefulness in acute painful knees
• guarding can mask laxity
• does not identify exact injured structure
• may not reproduce dynamic sport instability

Practical Applications

The Slocum Test may help professionals:

• assess anterior tibial translation with rotational bias
• explore anteromedial and anterolateral instability patterns
• compare involved and uninvolved knees
• document baseline rotational laxity response
• guide further ligament testing
• support referral or imaging discussion where appropriate
• communicate assessment findings with allied health or sports medicine teams

For athletes, it may contribute to broader return-to-training reasoning when combined with:

• strength testing
• hop testing
• landing assessment
• change-of-direction assessment
• confidence measures
• sport-specific movement assessment

For general population clients, it may help explore giving-way symptoms during twisting, pivoting or uneven-ground movement.

For Measurz users, the main value is structured recording of test variation, side, translation, endpoint, rotational position and related findings.

How to Record This in Measurz

Record:

• test name: Slocum Test
• side tested: left, right or both
• result: positive, negative, unclear or unable to test
• variation used: internal tibial rotation or external tibial rotation
• suspected pattern: anterolateral or anteromedial rotary instability
• client position
• knee flexion angle
• foot stabilisation method
• force direction: anterior tibial translation
• amount of anterior translation if estimated
• endpoint quality: firm, soft or absent
• rotational laxity observed
• pain score from 0–10
• symptom location
• symptom quality
• whether symptoms were familiar
• guarding or hamstring contraction
• comparison side
• irritability level
• reason for stopping if stopped early
• related findings, such as Lachman, Anterior Drawer, Pivot Shift, varus/valgus stress or swelling
• interpretation notes
• planned retest date if monitoring change

Record whether the main response was:

• increased anterior translation
• increased rotational laxity
• soft endpoint
• familiar instability
• pain only
• guarding
• unclear response
• unable to test safely

This improves:

• repeatability
• communication
• client education
• assessment reasoning
• team consistency
• progress monitoring
• reporting quality

Related Tests / Internal Links

• Lachman Test
• Anterior Drawer Test
• Pivot Shift Test
• Posterior Drawer Test
• Varus Stress Test
• Valgus Stress Test
• Sweep Test
• Knee Range of Motion Tests

FAQs

What does the Slocum Test assess?

It assesses anterior tibial translation with tibial rotation to explore anteromedial or anterolateral rotatory knee instability.

What is a positive Slocum Test?

A positive result may include increased anterior translation, increased rotational laxity, soft endpoint or a clear side-to-side difference.

Does a positive Slocum Test confirm an ACL injury?

No. A positive result may increase suspicion of rotational knee instability or ACL-related laxity, but it does not confirm a specific injury on its own.

Does a negative Slocum Test exclude knee instability?

No. A negative result does not fully exclude ACL injury or rotational instability, especially if symptoms only occur during faster or sport-specific movement.

How is the Slocum Test different from the Anterior Drawer Test?

The Anterior Drawer Test assesses anterior tibial translation with the knee flexed. The Slocum Test adds tibial rotation to bias different rotational instability patterns.

Are sensitivity and specificity available for the Slocum Test?

High-quality published sensitivity, specificity and likelihood ratio values for the exact Slocum Test appear limited. It should be interpreted alongside other knee findings.

What should the Slocum Test be used with?

It is best used with history, Lachman Test, Anterior Drawer Test, Pivot Shift Test, collateral ligament testing, swelling assessment and functional movement testing.

Key Takeaways

• The Slocum Test is a modified anterior drawer-style test.
• It uses tibial rotation to assess anteromedial or anterolateral rotatory instability.
• A positive result may include increased anterior translation, rotational laxity or a soft endpoint.
• The test does not confirm ACL injury or a specific ligament injury on its own.
• Published diagnostic accuracy evidence for the exact Slocum Test appears limited.
• Interpretation is stronger when combined with history, Lachman, Anterior Drawer, Pivot Shift, collateral tests, functional assessment and imaging where relevant.
• Measurz should record side, rotation variation, result, translation, endpoint quality, symptoms, guarding, comparison side and related findings.

References

Hughes, J. D., Rauer, T., Gibbs, C. M., & Musahl, V. (2019). Diagnosis and treatment of rotatory knee instability. Journal of Experimental Orthopaedics, 6, 48. https://doi.org/10.1186/s40634-019-0217-1

KneeGuru. (2024). Slocum test. https://www.kneeguru.co.uk/knee-a-to-z/slocum-test/

Physiopedia. (n.d.). Slocum’s test. https://www.physio-pedia.com/Slocum%27s_Test

Tanaka, M. J., et al. (2022). Diagnostic accuracy of physical examination tests for suspected acute anterior cruciate ligament injury: A systematic review and meta-analysis. International Journal of Sports Physical Therapy, 17(4), 606–615. https://ijspt.scholasticahq.com/article/36434-diagnostic-accuracy-of-physical-examination-tests-for-suspected-acute-anterior-cruciate-ligament-injury-a-systematic-review-and-meta-analysis

van Eck, C. F., van den Bekerom, M. P. J., Fu, F. H., Poolman, R. W., & Kerkhoffs, G. M. M. J. (2022). The diagnostic accuracy of clinical tests for anterior cruciate ligament injury. Knee Surgery, Sports Traumatology, Arthroscopy, 30, 3283–3292. https://doi.org/10.1007/s00167-022-06898-4