The Anterior Drawer Test is a physical examination technique used by healthcare professionals in orthopedics and sports medicine. This maneuver is performed to assess the stability of the knee joint following an injury. It is a common procedure administered after acute knee trauma, such as a sports-related twist or fall, where a ligament sprain or tear is suspected. The test involves a specific manipulation of the lower leg to check for excessive forward movement of the shin bone relative to the thigh bone. The goal is to gain an initial clinical impression of the extent of damage to the structures that normally limit this movement.
The Primary Target Structure
The Anterior Drawer Test specifically evaluates the integrity of the Anterior Cruciate Ligament (ACL). This ligament is one of four major bands of dense connective tissue that crisscross within the center of the knee joint, connecting the femur (thigh bone) to the tibia (shin bone). The ACL is oriented diagonally and functions primarily to prevent the tibia from sliding too far forward relative to the femur, a movement known as anterior translation. It also plays a significant role in limiting rotational instability in the knee.
Injuries to this ligament are particularly frequent in athletes participating in high-velocity sports that involve sudden stops, changes in direction, or pivoting movements, such as soccer, basketball, and skiing. When the ligament is subjected to forces beyond its tensile strength, it can sustain a partial sprain or a complete rupture, leading to instability in the joint. The test is designed to physically replicate the stress that the ACL normally resists, allowing the examiner to feel for any abnormal movement that suggests damage.
Performing the Test
A healthcare provider administers the Anterior Drawer Test with the patient lying on their back, a position known as supine. The patient’s hip is typically flexed to about 45 degrees, and the knee being examined is bent to a 90-degree angle. This specific positioning helps relax the hamstring muscles, which could otherwise mask the instability caused by a torn ligament.
The examiner stabilizes the patient’s foot by sitting gently on it or placing it against the exam table. With the foot secured, the provider uses both hands to grasp the proximal tibia just below the knee joint line. The thumbs are often placed along the joint line on either side of the patellar tendon to feel for movement. A gentle force is then applied to the tibia, pulling it directly forward, or anteriorly, toward the examiner. The provider is feeling for the amount of forward displacement of the tibia and the quality of the “end feel” when the movement stops.
Interpreting the Findings
The interpretation of the Anterior Drawer Test centers on comparing the movement of the injured knee to the healthy, uninjured knee. A “negative” result occurs when the movement of the tibia is minimal and is stopped abruptly by a firm sensation, which indicates that the ligament is intact and resisting the anterior pull. Normal movement typically involves less than 5 millimeters of forward tibial movement.
A “positive” result is characterized by excessive forward translation of the tibia compared to the opposite knee. This excessive movement suggests a tear or significant laxity in the ACL. An absent or “soft” endpoint, where the forward movement is not suddenly checked by a firm stop, is a strong indicator of a complete ligament rupture. Clinicians often grade the severity of the laxity based on the degree of displacement:
- Grade 1 involves mild laxity (1–5 mm).
- Grade 2 shows moderate laxity (5–10 mm).
- Grade 3 indicates severe laxity (over 10 mm).
Context and Limitations
While the Anterior Drawer Test is a component of a knee examination, its accuracy can be limited, particularly in the acute phase following an injury. Significant pain and swelling in the knee can cause the surrounding muscles, especially the hamstrings, to tense up, a reaction known as muscle guarding. This muscle tension can artificially restrict the forward movement of the tibia, leading to a false negative result where an ACL tear is present but not detected.
Because of this limitation, the Lachman Test is often considered a more sensitive alternative, particularly for acute injuries. The Lachman Test is performed with the knee bent to a lesser degree, typically 20 to 30 degrees of flexion, which helps to minimize the effect of muscle guarding. Despite the clinical utility of physical tests, a definitive diagnosis of an ACL tear and the full extent of any associated damage requires medical imaging, most commonly a magnetic resonance imaging (MRI) scan.