What is a Lachman Test?

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  • Written By: Malcolm Tatum
  • Edited By: Bronwyn Harris
  • Last Modified Date: 10 October 2019
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The Lachman test is a type of medical examination that is used to test the degree of flexibility of the knee and the range of motion for the anterior cruciate ligament that runs along the tibia. The purpose behind the test is to determine if there is any injury to the ligament, including a tear. The Lachman knee test is considered to be the most efficient and most accurate means of diagnosing problems with the anterior cruciate ligament, and is used extensively in sports medicine.

Named for John Lachman, an orthopedic surgeon who perfected the technique, the basics of the test involve positioning the patient in a prone position on an exam table. To begin the examination, the patient’s knee must be flexed to a point of roughly twenty to thirty degrees. The individual conducting the examination places one hand behind the tibia. The other hand is positioned on the thigh of the patient.

The next portion of the Lachman test makes it possible to begin the examination of the anterior cruciate ligament. While slowly pulling on the tibia, the examiner notes the performance of the ligament. If the ligament is intact and in proper working order, it will limit the range of motion to a normal amount. In the event that the ligament is torn, there will be an excessive amount of movement, as well as an endpoint that is somewhat soft to the touch.


When a Lachman test indicates the presence of a torn anterior cruiciate ligament, the result is know as a positive test. If the knee, tibia, and ligament function within an acceptable range of motion, this is known as a negative Lachman test, indicating that there are no rips, tears, or other serious damage present. The test makes it possible to eliminate a torn ligament as a cause for any knee pain present, and allows the attending physician to look into other potential reasons for the discomfort.

Practitioners of sports medicine are well-acquainted with the administration of the Lachman test. Professional athletes are at high risk for injuries to the legs and knees. Early detection of emerging problems with the tibia and the ligaments surrounding the tibia allows treatment to begin immediately, which in turn can often shorten the recuperative period. For this reason, team doctors often include this test as part of the regular checkups provided to each player.

Orthopedic physicians also make use of the Lachman test on an ongoing basis. The nature of the test makes it possible to determine if a problem is developing that will eventually impact the natural range of motion of the knee and tibia. By identifying the health issue early on, it is sometimes possible to relieve pressure on the ligament before a complete break takes place, and thus avoid surgery.


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