The posterior drawer test checks for damage to the posterior cruciate ligament (PCL), a thick band of tissue deep inside the knee joint. It is considered the most accurate hands-on clinical test for detecting PCL laxity, and it works by measuring how far the shinbone slides backward under the thighbone when force is applied.
What the PCL Does in Your Knee
The posterior cruciate ligament connects your thighbone (femur) to your shinbone (tibia) inside the knee. Its primary job is to prevent the tibia from sliding too far backward relative to the femur. It acts as one of the knee’s main stabilizers, and it does this through two separate bundles of fibers that work at different angles of knee flexion. When the PCL tears, either partially or completely, the tibia can shift backward more than it should. That abnormal movement is exactly what the posterior drawer test is designed to detect.
How the Test Is Performed
You lie on your back with the injured knee bent to about 90 degrees and your foot flat on the table. The examiner sits lightly on your toes to keep your foot from moving. They then wrap both hands around the top of your shinbone, placing their thumbs on the bony bump just below your kneecap (the tibial tuberosity).
From that position, the examiner pushes your lower leg straight backward and feels how much the tibia translates posteriorly. They compare the movement to your uninjured knee. If the shinbone slides noticeably farther back than normal, the test is positive, indicating PCL damage.
What the Results Mean
PCL injuries identified by the posterior drawer test are graded on a three-level scale based on how many millimeters the tibia shifts backward:
- Grade I (partial tear): 1 to 5 mm of posterior translation. The front edge of the tibia still sits ahead of the femoral condyles (the rounded ends of the thighbone). This indicates the ligament is stretched or partially torn but still provides some stability.
- Grade II (complete isolated tear): 6 to 10 mm of posterior translation. The front of the tibia lines up flush with the femoral condyles. The PCL is fully torn, but no other major ligaments are damaged.
- Grade III (complete tear with additional damage): More than 10 mm of posterior translation. The tibia drops behind the femoral condyles. This level of laxity typically means other ligaments or joint capsule structures are also injured.
Grade III results are particularly significant because they point to a multi-ligament knee injury, not just an isolated PCL tear. That distinction changes the treatment approach considerably.
How Accurate the Test Is
Among the various hands-on tests for PCL problems, the posterior drawer test has been found to be the most accurate. However, it does have a notable limitation: it generally requires significant posterior laxity to come back positive, meaning it works best for complete PCL tears. Partial tears with only mild looseness can sometimes produce a negative or ambiguous result.
For that reason, clinicians rarely rely on a single test. The posterior sag test (also called Godfrey’s test), the quadriceps activation test, and the dynamic posterior shift test all evaluate PCL integrity in slightly different ways. Using multiple tests together improves diagnostic confidence. Imaging, particularly MRI and stress X-rays that measure side-to-side differences in tibial translation, typically follows the physical exam to confirm the diagnosis and guide treatment decisions.
Why the Test Matters for Treatment
The grading information from the posterior drawer test directly influences whether you’ll need surgery. Current clinical standards generally recommend surgical intervention for grade II or higher PCL injuries, particularly when stress X-rays show 8 mm or more of posterior tibial translation compared to the other knee. Grade I injuries, where the ligament is only partially torn, are more often managed with physical therapy and rehabilitation focused on strengthening the quadriceps, which help compensate for the weakened PCL by pulling the tibia forward.
A comprehensive evaluation goes beyond just the posterior drawer test. Your clinician will take a full history of the injury (dashboard injuries in car accidents and direct blows to the front of the bent knee are the classic mechanisms), perform multiple physical exam maneuvers, and order imaging before recommending a treatment path. But the posterior drawer test remains the starting point and the single most informative bedside test for identifying PCL damage.