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The Lachman test is a clinical examination test destined to diagnose injuries associated to the anterior cruciate ligament (ACL). It consists of maintaining the femur in position while forcing the tibia into a translation movement towards the clinician. A significant displacement differencial between both knees usually indicates an injured ACL. Watch the video below to see how it is performed.
Video explanation:
In this video, the first Lachman test that is performed is negative as the clinician feels that the tibia is held backwards even though he applies a force on the tibia. However, the second test performed is a positive Lachman Test, as the tibia is not held back when applying the translation movement.
The knee is positioned in a 15-25° flexion. The examiner places one hand behind the tibia and the other on the patient's thigh. The examiner's thumb should be placed on the tibial tuberosity. Once correct positioning of both hands in done, the tibia is pulled forward to assess the amount of anterior translation of the tibia in comparison of the femur.
An intact ACL should prevent the anterior translation from happening (a firm endpoint can be felt) while an ACL-deficient knee will demonstrate an increased anterior translation. The so-called firm end point is also absent if the ACL is torn.
This test is usually considered reliable, sensitive and superior to the anterior drawer test. However, in the continuity of what is indicated in the video, it relies on many subjective factors such as:
It is therefore recommended to apply other objective methods of ACL assessment such as using an arthrometer to confirm the diagnosis or follow the state of the ACL graft over time after surgery.
Below are the main advantages of using arthrometers for treating injuries related to the ACL:
To learn more on these advantages, read our article explaining how arthrometers enhance the treatment delivered to patients suffering from knee ligament injuries or