Dr. Ebraheim’s educational animated video describes ACL injury examination - LACHMAN TEST.
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Lachman Test ACL Injury- Everything You Need To Know
Lachman’s test is the most sensitive examination test for the ACL injury. The anterior cruciate ligament is located in the front of the knee. The primary function of the ACL is to resist anterior translation of the tibia relative to the femur and provide some rotational stability to the knee. Rupture of the anterior cruciate ligament (ACL) is a condition commonly seen in sports due to a non-contact pivoting injury. ACL rupture is usually a complete rupture.
Patient Evaluation
• Patient usually feels or hears a “POP” within the knee.
• Sudden knee pain.
• Swelling within hours.
• The patient gives a history of the knee “giving away”.
• Exam is usually difficult and limited by the pain.
• There is usually hemorrhage within the knee joint (hemarthrosis).
If aspiration of the knee shows hemarthrosis, then there is a 75% chance of an ACL tear and a meniscal injury (usually the lateral meniscus). The Lachman test is the most useful and sensitive test for the diagnosis of ACL tear in the acute setting. To perform the Lachman test, the patient should be lying supine and completely relaxed. Ensure that the patient’s hip muscles, quadriceps, and hamstring muscles are all relaxed. Bend the knee to about 20-30 degrees. Stabilize the femur with one hand and with the other hand, pull the tibia anteriorly and posteriorly against the femur. With an intact ACL, as the tibia is pulled forward, the examiner should feel an end point. With an ACL rupture, the ACL will be lax, and the examination will feel softer with no endpoint. The tibia can be pulled forward more than normal (anterior translation). A sense of increased movement and lack of a solid end point indicates an ACL injury. Lachman’s test is the best examination test to diagnose a tear of the ACL. Be aware that a PCL tear may give posterior subluxation of the tibia and gives a false positive Lachman’s test.
ACL Injury Grades Using the Lachman’s Test
• Grade I
o 3-5mm of translation
• Grade II
o 5-10mm of translation
• Grade III
o More than 10mm of translation
In addition to assessing the amount of translation of the tibia and the quality of the end point of the Lachman exam, you will need to examine the patellar tendon and quadriceps tendons, because rupture of the ACL and rupture of these tendons may be confused with each other. Other tests may diagnose an ACL tear, but they are not as good as the Lachman test.
Other Tests for Diagnosis of ACL Tear
• Anterior Drawer Test
o Not as reliable as the Lachman Test
• Pivot Shift Test
o Done by going from extension to flexion of the knee, and the tibia will be reduced at 20-30 degrees of flexion.
o This test measures the functional instability of the knee, the “giving away” of the knee.
o Pivot shift is pathognomic for an ACL tear and is best demonstrated in a chronic setting.
o Pivot shift test is a more difficult test than the Lachman Test.
Rupture of the ACL causes anterolateral rotatory instability. The tibia moves anterolaterally in extension, however when you flex the knee, the IT band becomes a flexor of the knee. The IT band pulls back and reduces the tibia. The pivot shift test goes from extension (tibia sublexed) to flexion, with the tibia reduced by the iliotibial band. Both the Lachman Test and the Pivot Shift Test are associated with 20-30 degrees of knee flexion. The Lachman Test starts at 20-30 degrees of flexion. With the Pivot Shift Test, you feel the clunk at 20-30 degrees of flexion. So it seems that 20-30 degrees of flexion is important for examination of the ACL. Usually the diagnosis of ACL rupture is confirmed with an MRI. In addition to the ACL tear, the MRI of the knee joint can show bone bruises or injuries that can be consistent with an ACL tear. These injuries are typically located at the middle of the femoral condyle and the posterior part of the tibia laterally.
https://www.youtube.com/watch?v=OfszTOO5Ahg