HiA content is written by people who have worked inside Singapore's private healthcare system, and reviewed by qualified doctors before it is published.
We use peer-reviewed medical research, Ministry of Health guidance, and the direct clinical knowledge of our reviewers. We have no commercial interest in steering you toward a particular clinic, specialist, or treatment.
Key Takeaways
- The Lachman test checks whether your ACL may be injured by assessing forward movement of your shinbone in relation to your thighbone.
- A positive Lachman test may indicate ACL laxity or a tear, especially when there is increased movement and a soft endpoint.
- Your result should be interpreted alongside your symptoms, other knee tests and imaging when clinically appropriate.
Have you twisted your knee during sport, heard a pop, or felt it give way when you tried to stand? Are you wondering why a doctor or physiotherapist moved your shinbone while holding your thigh still?
The Lachman test is one of the clinical tests used when an anterior cruciate ligament (ACL) injury is suspected.
Knowing what the test checks, what a positive result may mean and what happens next can help you feel more prepared for your knee assessment and recovery journey.
What is the Lachman test for an ACL injury?
The Lachman test is a hands-on knee examination used to assess whether your ACL may be torn, partially torn or functionally lax.
Your ACL is one of the two cruciate ligaments inside the knee. It connects your thighbone, called the femur, to your shinbone, called the tibia. It helps prevent the tibia from moving too far forwards and contributes to knee stability during pivoting, landing and sudden changes in direction.
During the test, a clinician checks whether your tibia moves forwards more than expected in relation to your femur. This movement is called anterior tibial translation. Some movement is normal, but excessive movement or a soft or poorly defined endpoint may raise suspicion of an ACL injury, but does not confirm one on its own.
The Lachman test is commonly used after a sports injury, fall, collision or sudden knee twist. It is particularly relevant if you experience knee swelling, pain, instability or a feeling that your knee may buckle beneath you.
Why might you need a Lachman test?
Your doctor may perform a Lachman test if you have symptoms such as knee instability, swelling, or difficulty putting weight on your leg after an injury.
You may need a Lachman test if your symptoms or the way you injured your knee suggest a possible ACL tear.
ACL injuries often occur during activities that involve pivoting, stopping suddenly, jumping or landing awkwardly. Football, basketball, skiing and racquet sports are common examples, but an ACL injury can also happen during a fall, road traffic accident or everyday twisting injury.
A clinician may perform the Lachman test if you have:
- Heard or felt a pop at the time of injury
- Developed knee swelling soon after an injury
- Felt your knee give way, buckle or feel unstable
- Had pain after twisting or pivoting on your leg
- Found it difficult to continue playing sport
- Struggled to bear weight after the injury
- Experienced repeated episodes of instability during walking, turning or using stairs
These symptoms do not always mean that you have an ACL tear. Meniscus tears, cartilage injuries, kneecap problems and other ligament injuries can cause similar symptoms. Your clinician will consider your injury history, symptoms and a full knee examination before reaching a diagnosis.
How is the Lachman test performed?
During a Lachman test, the doctor stabilises your thigh and gently moves your lower leg forward to check for abnormal movement of the knee.
The Lachman test is usually performed while you lie on your back with your affected knee slightly bent, typically at around 20 to 30 degrees.
This position helps the clinician assess the ACL while reducing the influence of other structures around the knee. You do not usually need special preparation, equipment or an injection for the test.
During the examination, your clinician will generally:
- Ask you to lie comfortably on the examination couch.
- Position your knee in a slight bend.
- Stabilise your lower thigh with one hand.
- Hold the upper part of your shinbone with the other hand.
- Apply a gentle forward pull to the tibia.
- Compare the movement and feel of the injured knee with your unaffected knee.
The clinician is assessing two main features: how far your tibia moves forwards and whether there is a clear stopping point at the end of the movement. You may feel pressure or mild discomfort, particularly if your knee is painful or swollen, but the test should be performed gently.
What does a positive Lachman test mean?
A positive Lachman test means that your shinbone moves forwards more than expected or that the movement stops with a soft rather than firm endpoint.
A healthy ACL usually creates a distinct, firm endpoint when the tibia is drawn forwards. You can think of it as a strong restraint that limits excessive forward movement. If the ACL is torn or significantly stretched, the clinician may feel more movement and less clear resistance.
A positive result may raise concern for:
- A partial ACL tear
- A complete ACL tear
- ACL laxity, meaning the ligament is too loose
- An injury involving the ACL and other knee structures
However, a positive Lachman test does not confirm the exact type or severity of your injury on its own. Your clinician may use the result alongside your symptoms, injury mechanism, other knee tests and imaging, such as an MRI scan, when appropriate.
For example, if you twisted your knee while changing direction, felt a pop, developed swelling and now experience repeated knee buckling, a positive Lachman test may increase suspicion of an ACL injury. Further assessment can help identify whether there is also a meniscus, cartilage or other ligament injury.
What is the difference between a firm and soft endpoint?
A firm endpoint suggests that the ACL is providing a clear restraint against excessive forward movement of the tibia.
When your ACL is intact, the examiner usually feels a definite stop as the tibia reaches the limit of its normal movement. This is often described as a firm endpoint or firm end-feel.
A soft, mushy or absent endpoint may suggest that the ACL is not providing its usual restraint. This finding is more concerning when there is also noticeably greater forward movement compared with your other knee.
Your clinician will compare both knees because natural joint looseness varies between people. Some people have more flexible joints, while others have less movement in both knees. Comparing the injured side with the uninjured side helps make the assessment more meaningful.
How is the Lachman test graded?
The Lachman test may be graded according to the amount of forward movement in your tibia and the quality of the endpoint.
Grading systems can vary between clinicians, so the grade should always be interpreted together with your symptoms and other examination findings.
A higher grade does not automatically determine whether you need surgery. Your treatment plan depends on the full injury pattern, your level of instability, daily activities, sporting goals and response to rehabilitation.
Is the Lachman test accurate for diagnosing an ACL tear?
The Lachman test is a useful clinical assessment for suspected ACL injuries, but it cannot diagnose every ACL tear with complete certainty.
Research has found that the test has good diagnostic value, although reported accuracy differs across studies. A 2022 systematic review found pooled sensitivity of 79% and specificity of 91% for the Lachman test, while another review reported pooled sensitivity of 81% and specificity of 85%.
In simple terms, the test is helpful for identifying many ACL injuries, but a normal or unclear result does not always rule one out.
Several factors can affect the result:
- Pain that prevents you from relaxing your leg
- Knee swelling after a recent injury
- Muscle guarding, where your muscles tense to protect the joint
- A partial rather than complete ACL tear
- Other ligament, meniscus or cartilage injuries
- Differences in examination technique and clinical experience
- A larger or more muscular thigh, which may make positioning more difficult
For this reason, the Lachman test should be considered part of a complete assessment rather than a stand-alone answer. An orthopaedic specialist may recommend an MRI if it would help confirm an ACL tear or assess related injuries within the knee.
How does the Lachman test compare with other ACL tests?
The Lachman test is one of several tests used to assess ACL stability, with other knee examinations providing additional information about the injury.
The Lachman test is often used with other knee examinations because different tests assess different aspects of knee stability.
The anterior drawer test is performed with the knee bent more deeply, usually near 90 degrees. At this angle, other knee structures and muscle activity may influence the finding.
The pivot shift test assesses rotational instability, which can be important in ACL injuries. Evidence suggests that the pivot shift test can be highly specific when positive, while the Lachman test remains widely used for assessing suspected ACL rupture.
What happens after a positive Lachman test?
A positive Lachman test usually leads to a more complete knee assessment rather than an immediate treatment decision.
Your clinician may first ask more about how the injury occurred, whether your knee swelled quickly, whether it has buckled and what activities you want to return to. They may also check your range of motion, strength, walking pattern and signs of injury to other parts of the knee.
Your next steps may include:
- Further clinical tests: Your clinician may assess other ligaments, the meniscus and kneecap stability.
- Imaging: An X-ray may be used after trauma to look for bone injury. An MRI scan may be considered to evaluate the ACL, meniscus, cartilage and other soft tissues.
- Symptom management: You may be advised on activity modification, pain relief and managing swelling.
- Physiotherapy: Rehabilitation may help you restore knee movement, muscle strength, balance and confidence.
- Specialist review: An orthopaedic specialist can discuss whether non-surgical management or ACL reconstruction is more suitable for you.
Some people with ACL injuries can be managed with structured rehabilitation, particularly if they do not have persistent instability and do not regularly take part in pivoting sports. Others may consider ACL reconstruction if they have recurrent giving way, specific combined injuries or activity demands that require a more stable knee.
The appropriate option is individual and should be decided after a full assessment.
When should you seek urgent care for a knee injury?
You should seek urgent medical assessment if your knee injury causes severe symptoms or suggests a more serious injury.
Arrange prompt medical care if you have:
- A visibly deformed knee or suspected dislocation
- Severe swelling or rapidly worsening pain
- Inability to bear weight after significant trauma
- A foot that feels cold, numb, weak, pale or blue
- A knee that is locked and cannot fully straighten
- Fever, marked redness and warmth around a swollen knee
If your symptoms are less urgent but you have ongoing pain, recurrent knee buckling, swelling after activity or reduced confidence in your knee, arrange an assessment with an orthopaedic specialist or qualified healthcare professional.
Frequently asked questions
No. The Lachman test requires correct positioning, stabilisation of the thigh and comparison with the opposite knee. Attempting the test yourself may give an unreliable result and may worsen discomfort after an injury. A trained clinician should perform and interpret the examination.
The test may be uncomfortable if your knee is recently injured, swollen or very painful, but it should be performed gently. Let your clinician know if you are in significant pain or cannot relax your leg, as this can affect both your comfort and the result.
No. Whether you need an MRI depends on your symptoms, examination findings and whether imaging would help guide your treatment plan. MRI may be useful when the diagnosis is uncertain or when a clinician suspects associated meniscus, cartilage or ligament injuries.
You can seek assessment from an orthopaedic specialist, sports medicine doctor or a qualified clinician experienced in knee injuries. An orthopaedic specialist can assess ligament stability, arrange imaging if needed and discuss rehabilitation or surgical options based on your symptoms and goals.
Yes. Send us what you have. If anything's missing, we'll tell you exactly what to request and how.
Yes, the Care Team will remain your point of contact for follow-up appointments, questions about medication, transitions between specialists, and anything new that comes up.
Yes. Send us the report. We'll help you make sense of it, so you walk into the appointment with the right questions.
That’s a good outcome. It means you can move ahead with more confidence and stop second-guessing the plan.
Disclaimer
This article and its contents are provided for educational and informational purposes only and do not constitute medical advice or professional services specific to you or your medical condition. For decisions about your health or treatment, speak with a qualified doctor who knows your situation. An…
How we reviewed this article:
Health in Asia has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical journals and associations. We only use quality, credible sources to ensure content accuracy and integrity. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.
