Which test is commonly used to diagnose an ACL tear?

The Lachman test is commonly used to diagnose an anterior cruciate ligament (ACL) tear due to its sensitivity and specificity for this specific injury. During the test, the examiner stabilizes the femur while applying anterior translation to the tibia. If the ACL is intact, there will be a firm endpoint during this movement. However, if the ACL is torn, there will often be excessive translation of the tibia with a soft or absent endpoint, indicating failure of the ligament. This test is favored because it effectively isolates the ACL, making it a reliable indicator for diagnosing tears in this specific ligament.

While other tests like the McMurray's test and Thessaly's test are useful, they are primarily used to evaluate meniscal injuries rather than ACL tears. The antalgic test is more of a general assessment to determine if the patient is in pain and may alter their movement accordingly, but it does not specifically test for ACL integrity.