If both Lachman and anterior drawer signs are positive for ACL injury, MRI is usually unnecessary to confirm the diagnosis.

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Multiple Choice

If both Lachman and anterior drawer signs are positive for ACL injury, MRI is usually unnecessary to confirm the diagnosis.

When two reliable tests for ACL integrity are positive, the likelihood of an ACL rupture is already very high. The Lachman test, performed with the knee flexed about 20–30 degrees, is the most sensitive single clinical test for ACL injury and directly assesses anterior tibial translation. The anterior drawer test, done with the knee at 90 degrees, supports this finding by evaluating laxity as well. When both tests concordantly show laxity, there is strong clinical evidence of ACL rupture, making MRI primarily unnecessary for confirming the diagnosis. MRI remains useful if there is a need to evaluate associated injuries (such as meniscal tears or other ligament injuries) or to inform surgical planning, but it is not required to confirm an ACL tear when both signs are positive.

When two reliable tests for ACL integrity are positive, the likelihood of an ACL rupture is already very high. The Lachman test, performed with the knee flexed about 20–30 degrees, is the most sensitive single clinical test for ACL injury and directly assesses anterior tibial translation. The anterior drawer test, done with the knee at 90 degrees, supports this finding by evaluating laxity as well. When both tests concordantly show laxity, there is strong clinical evidence of ACL rupture, making MRI primarily unnecessary for confirming the diagnosis.

MRI remains useful if there is a need to evaluate associated injuries (such as meniscal tears or other ligament injuries) or to inform surgical planning, but it is not required to confirm an ACL tear when both signs are positive.

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