Posterior Drawer Test: How to Assess the Posterior Cruciate Ligament

The posterior cruciate ligament (PCL) is injured far less often than the ACL, but when it happens (typically from a direct blow to the shin, such as in a car accident or a fall onto a flexed knee) it can easily go unnoticed unless you specifically test for it. The posterior drawer test is the gold-standard maneuver for detecting it.

What does this test measure?

The posterior drawer test assesses posterior translation of the tibia relative to the femur with the knee flexed at 90°. This matters because, in PCL injuries, the tibia can "sag" backward under gravity even before any force is applied — which can be mistaken for an increased anterior drawer if you're not careful.

Equipment needed

• Treatment table
• No additional equipment required

Test protocol

1. The patient lies supine, with the hip flexed around 45° and the knee flexed at 90°, foot resting on the table
2. Before applying any force, look at the tibia in profile from the side: in a PCL injury, the tibia may appear "sunken" backward relative to the femur (posterior sag sign)
3. Place both hands around the proximal tibia, just as you would for the anterior drawer
4. Apply a gentle but firm posterior translation force, pushing the tibia backward
5. Assess the amount of displacement and the end-feel, comparing with the contralateral knee

Common mistakes

• Skipping the visual check of the tibia's profile before applying force (missing the posterior sag sign)
• Mistaking an increased posterior drawer for an anterior drawer if the tibia's neutral starting position wasn't correctly established
• Not comparing with the uninjured side

How to interpret the result

Result	Interpretation
No posterior "sag" of the tibia, displacement similar to the healthy side	Negative — PCL likely intact
Visible posterior sag sign + greater posterior displacement than the healthy side	Positive — suggests PCL injury
Mild posterior displacement, no clear sag sign	Inconclusive — assess alongside other findings (injury mechanism, posterior pain)

PCL injuries are often associated with other posterolateral or posteromedial structures, so a positive result warrants a more thorough medical evaluation, usually with an MRI.

Related tests

The posterior drawer is usually assessed together with:

• Anterior drawer test for the knee — to avoid confusing the two directions of instability
• Knee valgus/varus stress test — to rule out associated collateral ligament involvement

Document the injury mechanism

PCL injuries usually follow a characteristic mechanism (a direct blow to the shin with the knee flexed, for example in a car accident or a fall). With Movalytics you can log the posterior drawer result along with the injury context and mechanism, helping you build a complete, well-documented clinical history for follow-up.

Frequently asked questions

Are PCL injuries less severe than ACL injuries? Not necessarily less severe, but they are less common and, in many cases, can be managed conservatively if they're isolated and low-grade. The decision depends on the grade of the injury and whether other structures are involved. What is the "posterior sag sign"? It's the observation that the tibia, viewed in profile with the knee at 90°, appears displaced backward relative to the femur even before any force is applied, due to loss of PCL tension. Can a PCL injury go unnoticed? Yes, especially if it's isolated and low-grade, since symptoms can be less obvious than with an ACL injury. That's why it's important to include this test in your exam after trauma with a compatible mechanism.