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The drawer test is often administered by physicians when diagnosing a tear of the knee’s cruciate ligaments. The patient lies down flat on the examining table with his or her knees pulled up to a 90° angle. The physician, sitting on the patient’s feet, will pull the patient’s tibia either forward or backward depending on the type of drawer test being administered. A tibia that yields with greater ease than normal to the physician’s motions usually indicates that either the anterior or posterior cruciate ligament is torn. If the patient’s knee is at a 30° rather than 90° angle, the physician is performing a variation of the drawer test known as the Lachman test.
There are two types of this kind of test: anterior and posterior. The anterior drawer test is used to test for a tear of the anterior cruciate ligament. The posterior test assesses whether or not the posterior cruciate ligament is injured. Although it is most often performed on the knee, the drawer test can also be used on the ankle, shoulder, and elbow.
When performing this test, the examining physician usually instructs the patient to lie down flat on the examining table. The patient, with his or her feet flat on the table, draws the affected knee up to a 90° angle. Once the physician has verified that the patient’s hamstrings are relaxed, the doctor usually sits on the patient’s feet and grips the tibia. If performing an anterior drawer test, the physician will gently pull the tibia forward as though he or she were attempting to pull open a drawer. For a posterior test, the tibia is pushed back, as though the drawer were being closed.
If the patient’s tibia moves backward or forward more than what the normal range of motion should be, a cruciate ligament tear is likely. For most physicians, more than five millimeters of anterior or posterior motion will indicate a ligament injury. A drawer test yielding this type of result is viewed as positive.
The Lachman test is a variation of the drawer test. Rather than position the patient’s knee at a 90° angle, the physician places it at a 30° one. Once the femur has been stabilized, the physician grasps the tibia and gently pulls it towards, or pushes it away, from his — the doctor’s — body. The Lachman test is believed to be the more gentle of the two types of exams.
Treating a torn cruciate ligament depends on the severity of the injury. A mild tear may require rehabilitation rather than surgery. The goal is to strengthen nearby muscles to compensate for the injured ligament. A larger tear often requires reconstructive surgery and post-surgical rehabilitation. Regular exercise designed to strengthen the muscles surrounding the cruciate ligaments can help prevent ligament injury.