The Varus Stress Test is a knee special test used to assess lateral knee response when a varus force is applied to the tibiofemoral joint. It is most commonly used to support assessment reasoning around lateral collateral ligament involvement and, in some cases, broader posterolateral corner involvement.
A positive finding may include familiar lateral knee pain, increased lateral joint opening, or a softer end-feel compared with the other side. However, diagnostic accuracy evidence for the Varus Stress Test is limited, and the test should not be used as a stand-alone diagnostic tool.
The Varus Stress Test is a manual knee assessment used to observe the lateral knee’s response to varus loading. It is commonly associated with the lateral collateral ligament, also called the LCL.
The LCL helps resist varus stress at the knee. Testing at approximately 20–30 degrees of knee flexion is commonly used to place more emphasis on the LCL, while testing in full extension may provide information about broader lateral, capsular, cruciate or posterolateral corner involvement.
The test may be relevant after a direct blow to the inside of the knee, a varus force mechanism, pivoting injury, hyperextension-type trauma or sport collision. However, isolated LCL injuries are less common than many other knee injuries, and lateral knee instability may involve multiple structures.
A positive Varus Stress Test may increase suspicion of lateral knee ligament involvement when it matches the history and other findings. It does not confirm an LCL injury. A negative finding does not fully exclude lateral or posterolateral knee injury.
Test name: Varus Stress Test
Region: Knee
Primary structure assessed: Lateral collateral ligament and lateral knee structures
Common use: Lateral knee pain or suspected LCL/posterolateral involvement after trauma
Positive finding: Lateral knee pain, increased lateral joint opening, or softer end-feel compared with the other side
Negative finding: No relevant pain, no meaningful side-to-side laxity and firm end-feel
Common angles: Approximately 20–30 degrees knee flexion and full extension
Main limitation: Diagnostic accuracy evidence is limited and should be interpreted cautiously.
The Varus Stress Test is a manual knee assessment where the professional applies a varus force to the knee. In practical terms, the lower leg is moved inward relative to the thigh, creating stress through the lateral side of the knee.
The test is usually performed in two positions:
At approximately 20–30 degrees of knee flexion
This position is commonly used to assess the LCL more specifically.
In full knee extension
This position may suggest broader lateral, capsular, cruciate or posterolateral corner involvement if increased opening is present.
The professional observes and records pain, gapping, end-feel, side-to-side difference and symptom reproduction.
The Varus Stress Test may be used to support assessment reasoning around:
Lateral knee pain after trauma
Suspected LCL involvement
Possible posterolateral corner involvement
Varus or hyperextension injury mechanism
Direct blow to the inside of the knee
Side-to-side knee laxity comparison
Instability symptoms
Sport collision or twisting injuries
Whether further assessment may be appropriate
The test is useful because it is quick and clinically familiar. It is strongest when combined with history, palpation, swelling, range of motion, other ligament tests and functional assessment.
The Varus Stress Test assesses the knee’s response to varus loading.
It may provide information about:
Lateral knee pain response
Lateral joint opening
End-feel quality
Side-to-side laxity difference
LCL-related assessment reasoning
Possible posterolateral corner involvement
Irritability under varus load
It does not directly assess:
LCL fibre integrity with certainty
Posterolateral corner structure integrity with certainty
MRI findings
Meniscus status
ACL or PCL integrity
Strength
Running capacity
Readiness for sport or work
Tissue healing
Functional performance
The test may be useful for clients with:
Lateral knee pain after trauma
A varus or hyperextension mechanism
A direct blow to the inside of the knee
A feeling of lateral knee instability
Sport-related knee injury
Difficulty with pivoting, cutting or landing
Lateral knee symptoms during load-bearing tasks
A need for baseline or retest documentation in Measurz
It may also be useful for professionals learning how to structure lateral knee assessment.
Consider the Varus Stress Test when:
The injury mechanism suggests varus stress
The client reports lateral knee pain after trauma
LCL or posterolateral involvement is part of the assessment reasoning
You want to compare lateral laxity side to side
You need to document pain and end-feel under varus load
You are building a broader knee ligament assessment profile
It should usually be combined with other tests for ACL, PCL, posterolateral corner, meniscus, range of motion and functional performance where appropriate.
Use caution or avoid the test when:
There is suspected fracture
The knee is highly irritable or acutely swollen
The client cannot relax the limb
The client cannot tolerate manual stress
There is severe pain before testing
There are neurological symptoms
There is a major deformity or inability to bear weight after trauma
The professional is not confident the test can be performed safely
Stop the test if pain increases sharply, the client becomes distressed, the knee feels grossly unstable in a concerning way, or the client asks to stop.
The Varus Stress Test usually requires no equipment.
Optional equipment includes:
Measurz app
Pain rating scale
Treatment table or plinth
Towel roll or bolster
Video recording for education or comparison
Notes field for angle, pain, laxity and end-feel
Instrumented laxity or stress-imaging tools in specialist settings
Ask the client to lie supine on a plinth or firm surface.
Expose the knee enough to observe alignment, swelling and movement. Make sure the client is comfortable and relaxed.
Test the unaffected or less symptomatic side first where appropriate to understand the client’s normal end-feel.
The client lies supine with the tested knee relaxed.
For the 20–30-degree test:
Hip relaxed
Knee flexed to approximately 20–30 degrees
Lower leg supported
Foot and ankle relaxed
For the extension test:
Knee close to full extension
Limb relaxed
Avoid forced locking or hyperextension
The professional stands on the side of the tested leg.
One hand stabilises the medial side of the distal femur or knee region. The other hand controls the ankle or distal tibia.
For a right knee example:
Place one hand on the medial aspect of the knee or distal femur to stabilise.
Place the other hand around the distal tibia or ankle.
Keep the client’s limb relaxed.
Stabilise the thigh so the force is applied through the knee rather than rotating the whole limb.
The pelvis and hip should remain relaxed and neutral.
Apply a varus force to the knee.
This means the distal tibia is gently moved medially while the knee is stabilised, stressing the lateral side of the knee.
Apply the force gradually and compare with the opposite side.
Tell the client:
“Stay relaxed and let me move your leg. I am going to apply a gentle stress to the outside of the knee. Tell me if this reproduces your familiar symptoms and where you feel it.”
A positive finding may include:
Familiar lateral knee pain
Increased lateral joint opening compared with the other side
Softer or less distinct end-feel
Apprehension or symptom reproduction
Greater laxity at 20–30 degrees
Greater laxity in full extension suggesting broader involvement
Record whether the positive finding was based on pain, laxity, end-feel or a combination.
A negative finding may include:
No relevant lateral knee pain
No meaningful side-to-side laxity difference
Firm end-feel
No familiar symptom reproduction
Similar response to the opposite side
A negative finding does not fully exclude lateral knee injury.
Stop the test if:
Pain increases sharply
The client asks to stop
The client cannot relax
The knee feels grossly unstable
The professional cannot control the movement
The client experiences neurological symptoms
The test is not safe or meaningful
Use a gradual and controlled force. Do not bounce, jerk or force the knee. Acute knee injuries may be painful and guarded, so interpretation may be limited in early assessment.
A positive Varus Stress Test may increase suspicion of LCL or lateral knee structure involvement when it matches the client’s history, mechanism of injury and lateral knee symptoms. Pain without laxity may suggest a pain-dominant lateral knee response, while clear gapping or a softer end-feel may increase suspicion of structural laxity.
Increased opening at approximately 20–30 degrees may be more suggestive of LCL involvement. Increased opening in full extension may raise concern for broader involvement, including posterolateral, capsular or cruciate structures, but this must be interpreted cautiously.
A positive test does not confirm an LCL injury or posterolateral corner injury. Pain, guarding, swelling and other lateral knee structures may influence the finding.
A negative Varus Stress Test may reduce suspicion of clear lateral laxity, especially when history, palpation, swelling and functional assessment are also reassuring. However, it does not fully exclude lateral or posterolateral knee injury.
The finding is more meaningful when combined with:
Mechanism of injury
Lateral knee pain location
Swelling
Palpation findings
Range of motion
Other ligament tests
Posterolateral corner assessment
Gait and movement assessment
Functional testing
Imaging where relevant
High-quality diagnostic accuracy evidence for the Varus Stress Test appears limited.
One commonly cited study by Harilainen reported low sensitivity for the Varus Stress Test, around 25%, and specificity was not clearly reported in some summaries. This suggests that a negative manual Varus Stress Test should not be used on its own to exclude lateral collateral ligament involvement.
Condition or presentation: Acute knee ligament injury
Population: Acute knee ligament injury sample
Test variation: Varus stress testing for lateral ligament involvement
Reference standard: Compared with stress radiography, examination under anaesthesia, arthroscopic or operative findings in the broader study context
Sensitivity: Approximately 25% in commonly cited summaries
Specificity: Not clearly available in commonly cited summaries
Positive likelihood ratio: Not clearly available
Negative likelihood ratio: Not clearly available
Key limitation: Evidence is older, limited, and not sufficient for confident stand-alone interpretation.
Plain-language interpretation:
A positive result may increase suspicion if it matches the mechanism and other findings.
A negative result does not confidently exclude LCL or posterolateral involvement.
The test should be combined with broader knee assessment.
If symptoms, mechanism or functional instability remain concerning, further assessment may still be appropriate.
The Varus Stress Test has clinical face validity because it applies varus load to the knee and allows the professional to assess lateral pain, gapping and end-feel.
Reliability may be affected by:
Examiner experience
Acute pain and guarding
Knee flexion angle
Force magnitude
Hand placement
Client relaxation
Whether pain or laxity is used as the main positive finding
Difficulty detecting subtle lateral gapping manually
Validity as a stand-alone diagnostic test is limited. The test is more useful when combined with mechanism of injury, palpation, other ligament tests, posterolateral corner tests, movement assessment and imaging where relevant.
Instrumented stress methods or imaging may quantify lateral gapping more objectively in specialist settings, but manual testing remains a practical screening and assessment-reasoning tool.
Common errors include:
Testing only one angle
Applying force too aggressively
Not comparing with the opposite side
Not recording whether pain or laxity was positive
Ignoring end-feel quality
Testing while the client is guarding
Assuming pain means LCL injury
Assuming no laxity excludes LCL injury
Not assessing posterolateral corner involvement
Calling the test diagnostic
Limitations include:
Diagnostic accuracy evidence is limited
Manual force is difficult to standardise
Subtle laxity can be missed
Pain and swelling can limit assessment
Isolated LCL injury may be uncommon
Combined injuries may alter findings
A single test should not guide decisions alone
The Varus Stress Test may be useful for:
Lateral knee assessment
LCL-related assessment reasoning
Posterolateral corner screening context
Side-to-side laxity comparison
Baseline documentation
Retesting over time
Deciding whether further assessment may be needed
Communicating findings to clients
Supporting Measurz knee assessment reports
It is best used as part of a broader assessment that includes history, swelling, range of motion, palpation, gait, functional tasks and other ligament tests.
Record:
Test name: Varus Stress Test
Side tested
Knee angle: 20–30 degrees or full extension
Result: positive, negative, unclear or unable to test
Pain score
Symptom location
Pain quality
Laxity: none, mild, moderate or marked
End-feel: firm, soft or absent
Comparison side
Mechanism of injury
Irritability
Guarding or compensations
Reason for stopping if relevant
Related findings
Confidence in result
Further assessment or referral notes if appropriate
Retest date if relevant
Recording these details improves repeatability, communication, client education, assessment reasoning, monitoring over time, team consistency and reporting quality.
Valgus Stress Test
Lachman Test
Anterior Drawer Test
Posterior Drawer Test
Dial Test
Posterolateral Drawer Test
McMurray Test
Thessaly Test
Knee Girth
Knee Range of Motion
Hop testing
Balance testing
It assesses the knee’s response to varus load and is commonly used to support reasoning around LCL or lateral knee involvement.
A positive finding may include lateral knee pain, increased lateral joint opening or a softer end-feel compared with the other side.
Both may be useful. The flexed position is commonly used for LCL emphasis. Full extension may provide information about broader stabilising structures.
No. It may increase suspicion, but it does not confirm injury on its own.
No. Diagnostic accuracy evidence is limited, so a negative result does not fully exclude lateral knee involvement.
Yes, where relevant and within scope, especially if the mechanism or symptoms suggest broader lateral or posterolateral involvement.
It can be useful, but acute pain, swelling and guarding may limit interpretation.
History, mechanism, palpation, swelling, range of motion, other ligament tests, gait and functional assessment.
The Varus Stress Test is commonly used to assess lateral knee response to varus load.
Testing at 20–30 degrees and full extension provides different information.
Positive findings may include pain, gapping or altered end-feel.
Diagnostic accuracy evidence is limited, and the test should be interpreted cautiously.
A negative test does not confidently exclude LCL or posterolateral involvement.
Measurz recording should include angle, pain, laxity, end-feel and side-to-side comparison.
Harilainen, A., Myllynen, P., & Antila, H. (1986). Diagnosis of acute knee ligament injuries: The value of stress radiography compared with clinical examination, stability under anesthesia and arthroscopic or operative findings. Annales Chirurgiae et Gynaecologiae, 75, 37–43.
Harilainen, A. (1987). Evaluation of knee instability in acute ligamentous injuries. Annales Chirurgiae et Gynaecologiae, 76, 269–273.
Logerstedt, D. S., Scalzitti, D. A., Risberg, M. A., Engebretsen, L., Webster, K. E., Feller, J., Snyder-Mackler, L., & Axe, M. J. (2017). Knee stability and movement coordination impairments: Knee ligament sprain revision 2017. Journal of Orthopaedic & Sports Physical Therapy, 47(11), A1–A47. doi:10.2519/jospt.2017.0303
NICE. (2024). Knee pain — assessment: Examination. National Institute for Health and Care Excellence Clinical Knowledge Summaries.
Smith, T. O., Davies, L., & Hing, C. B. (2016). A systematic review to determine the reliability of knee joint clinical assessment tests. The Knee, 23(2), 219–228. doi:10.1016/j.knee.2015.06.010
Terry, G. C., & LaPrade, R. F. (1996). The posterolateral aspect of the knee: Anatomy and surgical approach. The American Journal of Sports Medicine, 24(6), 732–739. doi:10.1177/036354659602400606
