Anterior vs Posterior Drawer Test

What is an anterior drawer test of the knee?

The anterior drawer test of the knee is an important diagnostic tool used to assess the integrity of the anterior cruciate ligament (ACL). The ACL is one of the key ligaments that provide stability to the knee joint, preventing the tibia from sliding forward relative to the femur.

The purpose of the anterior drawer test is to test the ACL's current health, whether it is injured or not. Sudden stops, changes in direction, or direct impacts can result in an ACL tear, making it a particularly common injury among athletes. The test helps to determine whether the ligament is intact, partially torn, or completely ruptured.

How to do the anterior drawer test of the knee

These are the steps to perform the anterior drawer test for the knee:

1. The patient lies supine on a flat surface with the hips flexed to 45 degrees, the knees bent to 90 degrees, and the feet flat on the table.
2. The examiner sits on the toes of the tested leg to stabilize it.
3. The examiner grasps the lower leg just below the tibial plateau or joint line.
4. The examiner then attempts to move the lower leg forward, assessing the degree of anterior movement and end feel.

If the tibia moves forward significantly or if there's a lack of a firm end feel, the test is considered positive, suggesting potential damage to the ACL. A positive anterior drawer test indicates that the ACL is either partially or completely torn. A negative test indicates an uninjured knee.

However, this test should not be used in isolation for diagnosis. Additional assessments, such as the Lachman test or imaging like MRI, are often employed to confirm the extent of the injury.

When interpreting the results, it's important to consider the patient's overall clinical picture. A positive test might be associated with symptoms such as knee instability, pain, or a history of trauma. In some cases, patients with a positive test may have difficulty performing activities that involve pivoting or sudden directional changes.

What is a posterior drawer test?

The posterior drawer test of the knee is a clinical knee assessment designed to evaluate the integrity of the posterior cruciate ligament (PCL). The PCL is a crucial ligament in the knee that prevents the tibia from sliding backward relative to the femur.

The posterior drawer test assesses the health of the PCL. PCL injuries, while less common than ACL injuries, can occur due to traumatic events such as direct blows to the front of the knee or sudden hyperflexion. The test helps to identify potential PCL tears or laxity, which can result in knee instability and impair normal function.

How to do the posterior drawer test of the knee

To perform the posterior drawer test, do the following:

1. The patient should lie in a supine position with the knee to be tested flexed to approximately 90 degrees.
2. The examiner sits on the toes of the tested leg to stabilize it.
3. The examiner grasps the proximal lower leg at the tibial plateau or joint line, with the thumbs placed on the tibial tuberosity.
4. The examiner then attempts to move the lower leg backward, assessing the degree of posterior movement and end feel.

A positive posterior drawer test is indicated by the excessive backward movement of the tibia, or a lack of a firm end feel, suggesting damage to the PCL. This could mean that the PCL is partially or completely torn, leading to knee instability.

Conversely, a negative test indicates an intact PCL, where the tibia's backward movement is limited and there is a normal end feel.

Remember: this test is just one piece of the diagnostic puzzle. Additional assessments, such as the posterior sag sign, or imaging like MRI, may be necessary to confirm the extent of the injury. The test results should be interpreted in the context of the patient's symptoms, which might include knee instability, extreme pain, or a history of trauma.

Anterior vs  Posterior Drawer Test

Both the anterior and posterior drawer tests are used to assess the integrity of the cruciate ligaments in the knee. However, they target different knee ligaments and provide insights into different knee injuries. Let's take a closer look at the biggest differences between the two tests.

Targeted ligament

The two tests' names are the first clue; they assess different ligaments. The anterior drawer test evaluates the ACL, which prevents the tibia from sliding forward relative to the femur. The posterior drawer test examines the PCL, which stops the tibia from moving backward relative to the femur. The ACL is crucial for activities like running, while the PCL stabilizes the knee during actions like walking and descending stairs

Procedure

Both tests have the patient lying supine with the knee bent to 90 degrees, but the direction of the force applied differs. The anterior drawer test pulls the lower leg forward to check forward translation of the tibia, while the posterior drawer test pushes the lower leg backward to check backward translation. The hand positioning is similar, but the pressure direction changes.

Disorders/injuries they assess

The anterior drawer test primarily checks for ACL injuries, which can result from activities like sudden stops or changes in direction, which are common in sports. The posterior drawer test focuses on PCL injuries, often caused by direct trauma to the front of the knee or hyperflexion injuries.

Key takeaways

The anterior and posterior drawer tests are essential tools for evaluating knee injuries. These tests allow healthcare professionals to assess the stability of the knee's crucial ligaments—the ACL and the PCL.

Both tests involve the patient lying supine with the knee bent to 90 degrees, but their directional focus differs. The anterior drawer test pulls the tibia forward to evaluate the ACL, while the posterior drawer test pushes the tibia backward to assess the PCL.

A positive result in either test indicates ligament laxity or injury, with the degree of movement and lack of end, feel in the tibia determining the severity of the injury. The anterior drawer test identifies ACL injuries, which often result from sudden stops or changes in direction, while the posterior drawer test identifies PCL injuries, typically caused by direct trauma or hyperflexion.

Knowing the nuances and differences of these tests will enable you to diagnose and treat knee injuries accurately, ensuring optimal care and recovery for your patients. With this knowledge, you can support your patients effectively, whether they're athletes returning to their sport or individuals recovering from daily mishaps.

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