The posterior drawer test is a hands-on clinical examination used to detect injury to the posterior cruciate ligament (PCL), the thick band of tissue at the back of the knee that prevents the shinbone from sliding too far backward relative to the thighbone. A clinician performs it by pushing the top of the shin backward while the knee is bent at a right angle, feeling for abnormal looseness. The test is one of the most widely used bedside assessments for PCL damage, but it has real limitations, especially in partial tears and when swelling or muscle guarding obscure the findings.
What the PCL Does and Why It Matters
The PCL is the strongest ligament inside the knee joint, roughly twice as thick as the more commonly discussed anterior cruciate ligament (ACL). Its primary job is acting as the main restraint against the tibia (shinbone) shifting backward relative to the femur (thighbone).1PubMed Central. Posterior Cruciate Ligament: Anatomy and Biomechanics That backward shift is called posterior tibial translation, and the posterior drawer test is designed specifically to provoke and measure it. Because the PCL is the primary check on that movement, a torn or stretched PCL allows the tibia to move further back than it should, and the examiner can feel that excess motion with their hands.
PCL injuries are less common than ACL tears, but they are far from rare. They typically happen during car accidents (a “dashboard injury” where the bent knee strikes the dashboard), contact sports, and falls onto a flexed knee. Unlike ACL tears, which often produce an obvious pop and immediate instability, PCL injuries can be subtle. The knee may swell less dramatically, and the patient may walk away thinking they simply bruised it. That subtlety is exactly why a reliable physical examination matters.
How the Test Is Performed
You lie on your back on an examination table with the injured knee bent to roughly 90 degrees and your foot flat on the table. The examiner sits lightly on your foot to keep it from sliding, then wraps both hands around the upper part of your shin, just below the knee. From there, they push the tibia straight backward and feel how far it moves relative to the femur.
Before pushing, the examiner checks a reference point: the front edge of the tibial plateau (the flat top of the shinbone) normally sits about a centimeter or so forward of the femoral condyles (the rounded ends of the thighbone). If the tibia has already sagged backward before the examiner even pushes, that starting position is abnormal and the test may underestimate how much extra motion is truly present. This is why experienced clinicians always compare the injured knee with the healthy one and look at the resting position of the tibia first.
Grading the Results
Posterior drawer findings are graded on a scale from 0 to 3, based on how far the tibia moves backward and where it ends up relative to the femoral condyles:
- Grade 0: normal, no abnormal backward motion.
- Grade 1: the tibia shifts backward but still sits in front of the femoral condyles. This usually corresponds to a partial PCL tear.
- Grade 2: the tibia shifts backward until its front edge is flush with the femoral condyles. This is consistent with a complete PCL tear.
- Grade 3: the tibia slides past the femoral condyles, meaning other structures beyond the PCL are also damaged.
Cadaver studies have put numbers to these grades. In a systematic review pooling data from over 240 cadaveric knee specimens, cutting the PCL produced an average increase in backward tibial translation of about 11 mm during the posterior drawer maneuver. Intact knees in the same studies showed roughly 5 mm of baseline translation.2PubMed Central. Posterior tibial translation resulting from the posterior drawer manoeuver in cadaveric knee specimens: a systematic review In clinical studies of patients with confirmed complete PCL tears, stress radiographs showed an average of about 12 mm of posterior translation, while the posterior drawer test by hand measured roughly 9 mm of increased dropback.3PubMed. Diagnosis of complete and partial posterior cruciate ligament ruptures: Stress radiography compared with KT-1000 arthrometer and posterior drawer testing The gap between those numbers suggests the hands-on exam consistently underestimates the true laxity, which is one of its known weaknesses.
When the Test Can Be Misleading
The posterior drawer test works best for complete PCL tears, which produce enough laxity to feel clearly under the hands. The trouble comes with partial tears and with acute injuries where swelling and muscle spasm tighten the joint. Several clinical tests for the PCL, including the posterior drawer, require significant posterior laxity associated with complete PCL disruption to be positive.4PubMed Central. The diagnosis of PCL injury: literature review and introduction of two novel tests In other words, a negative posterior drawer does not rule out a PCL injury; it may simply mean the tear is partial or the joint is too guarded for the examiner to detect the motion.
Another pitfall involves misidentifying which ligament is injured. The posterior drawer test and the anterior drawer test (used for ACL injuries) can be confused if the examiner does not check the resting position of the tibia first. In a knee with a torn PCL, gravity pulls the tibia backward when the knee is bent. An unwary examiner might push the tibia forward from that sagged position, feel it return to its normal spot, and mistakenly call it a positive anterior drawer, diagnosing an ACL tear that doesn’t exist. This is a well-documented clinical trap, and it is one reason clinicians are taught to look for the posterior sag sign, the visible disappearance of the normal tibial prominence when the knee is bent at 90 degrees, before performing any drawer test.5PubMed Central. Injuries to the posterior cruciate ligament of the knee
The Role of Tibial Rotation During the Test
A nuance that separates a basic posterior drawer from a more informative one is what happens when the examiner rotates the foot inward or outward before pushing. The standard test is done with the foot pointing straight ahead (neutral rotation), but performing it with the tibia rotated internally or externally can reveal damage to structures beyond the PCL itself.
A recent biomechanical study using robotic testing found that performing the posterior drawer with the tibia rotated inward or outward actually reduced the measured backward translation in a PCL-deficient knee, because other structures around the knee tighten up and compensate. But when those peripheral stabilizers were also cut, the translation jumped dramatically. Damage to the structures on the outer back corner of the knee (the posterolateral corner) led to an additional increase of up to roughly 13 mm when the foot was rotated outward. Damage to the inner back corner structures (posteromedial corner) added up to about 15 mm when the foot was rotated inward.6PubMed Central. Restriction of Posterior Tibial Translation During the Posterior Drawer Test in Internal or External Rotation Is Dependent on Peripheral Stabilizers of the Knee: A Biomechanical Robotic Investigation
This is clinically meaningful because a knee with an isolated PCL tear behaves very differently from one with combined ligament injuries. In cadaver work, cutting the PCL alone produced a Grade 2 posterior drawer in every specimen, but adding a posterolateral corner injury pushed every specimen to a Grade 3 drawer. Posterior displacement roughly doubled, from about 13 mm to over 22 mm.7Journal of Bone and Joint Surgery. A Clinically Relevant Assessment of Posterior Cruciate Ligament and Posterolateral Corner Injuries So if a clinician finds a Grade 3 posterior drawer, it’s a strong signal that the PCL is not the only structure that needs attention.
Secondary Restraints You Can’t See
The PCL does not work alone. Inside the joint, the meniscofemoral ligaments (small ligaments running from the meniscus to the femur) act as backup restraints against posterior tibial translation. In an intact knee, these ligaments contribute about 28% of the total force resisting a posterior drawer at 90 degrees of flexion. When the PCL is torn, their contribution jumps to roughly 70%, because they become the main remaining check on backward motion.8The Journal of Bone and Joint Surgery. British volume. The meniscofemoral ligaments: secondary restraints to the posterior drawer This means that two patients with “the same” PCL tear can show very different amounts of laxity on the posterior drawer test, depending on whether their meniscofemoral ligaments are intact. The integrity of these small structures should ideally be assessed on MRI and during any arthroscopic procedure.9The Journal of Bone and Joint Surgery (British Volume). THE MENISCOFEMORAL LIGAMENTS ARE SECONDARY RESTRAINTS TO POSTERIOR DRAWER
Tibial slope, the natural angle of the top of the shinbone, also affects results. Studies have found that combined sectioning of the PCL and the posterolateral corner structures led to increases in posterior drawer of about 10.5 mm, with tibial slope influencing how much instability manifests during dynamic testing.10PubMed. The effect of proximal tibial slope on dynamic stability testing of the posterior cruciate ligament- and posterolateral corner-deficient knee In short, the posterior drawer test measures the combined behavior of several structures, not just the PCL in isolation.
Other Tests Used Alongside the Posterior Drawer
Clinicians rarely rely on a single test to diagnose a PCL injury. Several companion examinations are commonly used together:
- Posterior sag sign (Godfrey’s test): with the hip and knee both bent at 90 degrees while the patient lies on their back, the examiner looks from the side to see if the tibial prominence has dropped backward. This is considered the most characteristic finding in a PCL-ruptured knee and is checked before the posterior drawer to establish the starting position.
- Quadriceps active test: the patient lies with the knee at 90 degrees and is asked to contract the quadriceps muscle without extending the knee. In a PCL-deficient knee, the tibia visibly shifts forward as the quadriceps pull corrects the posterior sag.
- Dial test: compares external rotation of both tibias at 30 and 90 degrees of knee flexion to detect posterolateral corner injuries that often accompany PCL tears.
- Reverse Lachman test: similar to the posterior drawer but done at about 30 degrees of flexion rather than 90, which changes which fibers of the PCL are tested.
All of these tests share a common limitation: they tend to require substantial laxity to be clearly positive, which means they work best for complete tears and may miss partial injuries.4PubMed Central. The diagnosis of PCL injury: literature review and introduction of two novel tests This is why imaging, especially MRI, plays such a central role in confirming the diagnosis.
How MRI Findings Compare to the Physical Exam
MRI is the gold standard for confirming a PCL tear and assessing its severity. One study looking at patients with knee dislocations and multiple-ligament injuries found that when MRI showed the PCL as intact or only mildly injured, the knee was clinically stable on posterior drawer testing at the time of surgery about 99% of the time. But when MRI classified the PCL as partially or completely torn, the knee was unstable on posterior drawer testing only about 58% of the time.11PubMed. Can magnetic resonance imaging predict posterior drawer laxity at the time of surgery in patients with knee dislocation or multiple-ligament knee injury? That asymmetry underscores an important point: a normal MRI reliably predicts a stable posterior drawer, but an abnormal MRI does not always predict a positive drawer test. The hands-on exam and imaging each capture something the other may miss.
Researchers have also developed MRI-based versions of the posterior drawer, where the patient lies in the scanner with a load applied to the shin to simulate the examiner’s push. In these loaded MRI studies, complete PCL tears produced posterior translations in the range of about 13 mm, compared to around 7 mm in intact knees, and the displacement of the menisci tracked with the severity of PCL damage.12Scientific Reports. The MRI posterior drawer test to assess posterior cruciate ligament functionality and knee joint laxity These techniques are mostly used in research settings for now, but they offer a way to quantify laxity without the variability that comes from different examiners applying different amounts of force.
What the Test Results Mean for Treatment
The grade of laxity found on the posterior drawer directly influences whether you’re headed for rehabilitation or surgery. Isolated Grade 1 tears, those with less than about 8 mm of side-to-side difference on stress testing, are typically managed without surgery. Rehabilitation focuses on aggressive quadriceps strengthening, because the quadriceps muscle counteracts the backward pull on the tibia during everyday activities.13PubMed Central. Current standards for the objective assessment and management of posterior cruciate ligament tears: a narrative review
For isolated Grade 2 injuries, the picture is more nuanced. Nonsurgical management is generally recommended for isolated grade 1 or 2 PCL injuries, and even for grade 3 injuries in patients with mild symptoms or low activity demands. Surgery is typically reserved for high-demand athletes or for cases where conservative treatment hasn’t worked.14Journal of the American Academy of Orthopaedic Surgeons. Management of Posterior Cruciate Ligament Injuries: An Evidence-Based Review Combined injuries, where the posterior drawer shows Grade 3 laxity and other ligaments are also involved, almost always require surgical reconstruction.
It’s worth noting that the amount of laxity on the posterior drawer doesn’t always match how a patient feels. One study of patients managed without surgery found that those with greater posterior laxity on the drawer test tended to report more symptoms and dissatisfaction.15PubMed. Nonoperatively treated isolated posterior cruciate ligament injuries But another follow-up study found no statistically significant correlation between the grade of PCL laxity and patient-reported knee function scores.16PubMed Central. The nonoperative treatment of acute, isolated (partial or complete) posterior cruciate ligament-deficient knees: an intermediate-term follow-up study The disconnect likely reflects the influence of muscle strength, activity level, and individual anatomy on how a loose PCL translates into real-world function. Some people with a clearly positive posterior drawer manage to play recreational sports comfortably; others with the same test results struggle with stairs.
Using the Posterior Drawer After Surgery
The posterior drawer test doesn’t retire after a diagnosis is made. It’s one of the main ways surgeons track whether a PCL reconstruction has restored stability. Results after surgery are mixed but generally encouraging. Across studies of combined PCL reconstruction techniques, between 37% and 70% of patients had a normal (negative) posterior drawer at final follow-up.17Sports Medicine and Arthroscopy Review. Outcomes of Posterior Cruciate Ligament Treatment: A Review of the Evidence Some surgical approaches have reported higher success rates; one series using a specific reconstruction technique found that about 94% of patients had a negative posterior drawer at two or more years after surgery.18PubMed. Sandwich-style posterior cruciate ligament reconstruction
Even in patients who still have a mildly positive posterior drawer after reconstruction, functional outcomes can be good. Surgeons weigh the test result against knee function scores, patient satisfaction, and the ability to return to desired activities. A Grade 1 posterior drawer after surgery in someone who is pain-free and playing their sport is viewed very differently from the same finding in someone who feels unstable walking on uneven ground.
Why Examiner Technique Matters More Than You’d Think
Unlike imaging, which produces a picture that multiple people can review, the posterior drawer is inherently subjective. The amount of force the examiner applies, how relaxed the patient’s hamstrings are, and the examiner’s experience all influence the result. A nervous patient who can’t relax their leg will have tighter hamstrings pulling the tibia backward, potentially masking the very laxity the test is trying to find. Conversely, an examiner who doesn’t push firmly enough may miss a mild-to-moderate increase in translation.
The comparison between stress radiography and manual posterior drawer testing illustrates this gap. In the same group of patients with confirmed complete PCL tears, stress radiographs consistently measured more posterior translation than the clinician’s hands did.3PubMed. Diagnosis of complete and partial posterior cruciate ligament ruptures: Stress radiography compared with KT-1000 arthrometer and posterior drawer testing Stress radiography applies a standardized, measurable force and gives a number in millimeters, removing much of the subjectivity. Some practices use it routinely for preoperative planning and postoperative monitoring, while others rely primarily on the hands-on exam and MRI. In research settings, instrumented devices and robotic testing rigs can quantify posterior translation down to a fraction of a millimeter, but those tools aren’t practical in a clinic.
For the patient sitting on the table, the practical takeaway is that a single posterior drawer test by a single examiner on a single day is a useful but imperfect snapshot. If the clinical picture doesn’t match the test result, most orthopedic specialists will order additional imaging or repeat the exam under anesthesia, when muscle guarding is eliminated, before making treatment decisions.