Glossary
Lachman test
Quick answer
The Lachman test is a gentle hands-on examination in which the surgeon holds the thigh, bends the knee slightly and draws the shin forward to check whether the anterior cruciate ligament (ACL) stops it firmly. It is the most sensitive office test for an ACL tear, as Doha knee surgeon Dr. Pablo Gelber explains at Aman Hospital.
What the test involves
You lie on your back with the knee bent about 20 to 30 degrees, often resting over the surgeon's thigh or a pillow. One hand steadies your thigh just above the knee and the other holds the top of the shin. The surgeon then pulls the shin gently forward.
Most people feel a light pulling or a shifting sensation rather than pain. It helps to let the thigh muscles go completely loose, because tense hamstrings can hide a loose ligament.
What it tells the surgeon
A healthy ACL gives a firm, sudden stop, called a firm end point. A torn ACL lets the shin glide further forward and the stop feels soft or absent. The surgeon compares both knees, because natural laxity varies from person to person.
The test is graded by how far the shin moves and the quality of the stop. A clear soft end point, together with a story of a twist and swelling, strongly suggests an ACL tear even before any scan.
Limits and next steps
In the first days after an injury, swelling and guarding can make the test hard to read, so it may be repeated a week or two later. An MRI usually confirms the tear and shows any meniscus or cartilage injury alongside it, which shapes the treatment plan.
Frequently asked questions
Does the Lachman test hurt?
Usually not. Most patients feel a pulling or slipping sensation. A very fresh, swollen knee can be sore, which is why the test is sometimes repeated once swelling settles.
Can the Lachman test be normal with a torn ACL?
Occasionally, if the muscles are tense, the knee is very swollen or the tear is partial. That is why the examination is combined with your history and, when needed, an MRI.
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