Special Tests of the Knee Ligaments

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Overview of Knee Special Tests

Photo of a tennis player holding a painful knee.
Your PT may perform special tests for your knee pain. Westend61/Getty Images


The knee joint is stabilized by four important ligaments. These are the anterior cruciate ligament, posterior cruciate ligament, medial collateral ligament, and lateral collateral ligament.

Each separate ligament prevents excessive motion of the knee. The anterior cruciate ligament prevents excessive anterior glide of your shin under your thigh bone. The posterior cruciate ligament prevents excessive posterior motion of your shin below your femur. Your medial collateral ligament prevents excessive abduction of the tibia and guards an excessive force coming from the outside area of your knee.  Your lateral collateral ligament prevents excessive adduction of the tibia and guards against an excessive force coming from the inside aspect of your knee.

When damaged, your knee becomes unstable in the direction that the injured ligament stabilized. If you suspect that you have damaged a knee ligament, you must check in with your doctor to get an accurate picture of your condition and to start on the correct treatment. You may benefit from a visit with a physical therapist to assess your knee. He or she may perform knee special tests to check the integrity of your knee ligments. 

There are four special tests each to evaluate the four ligaments of your knee. Learn the names of these tests, the ligaments they evaluate, and how to perform them. Click through the steps of this program to learn more about knee special tests.

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Anterior Drawer Test

Learn how to determine if your ACL is torn.
Grasp the shin bone and slowly pull it towards you. Excessive motion may indicate an ACL tear. Brett Sears, PT, 2013

The anterior drawer test is used to assess the integrity of your anterior cruciate ligament (ACL). The test is performed by lying down on your back with your knee bent. Another person grasps your tibia just behind your knee and gently pulls forward. Excessive motion of your tibia underneath your femur indicates a positive test and an ACL tear may be suspected.

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Posterior Drawer Test

The posterior drawer test evaluates the posterior cruciate ligament. To perform this test, place the knee in ninety degrees of flexion with the patient laying supine and the foot stabilized on the table. Grasp the anterior aspect of the tibia over the tibial tuberosity and push forward (displacing the tibia posteriorly) with a steady force. If the tibia moves posteriorly more than normal (compare with the uninjured leg) the test is positive. This is indicative of a posterior cruciate ligament tear or injury.

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Valgus Stress Test

The valgus or abduction stress test evaluates the medial collateral ligament. To perform this test, place the knee in thirty degrees of flexion. While stabilizing the knee, press firmly against the outside portion of the knee while holding the ankle stable. If the knee gaps on the inner portion of the joint greater than normal (compare with the uninjured leg), the test is positive. This is indicative of a medical collateral ligament tear.

Often a "clunk" will be felt when perform the valgus stress test if the medial collateral ligament is injured.

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Varus Stress Test

The varus or adduction stress test evaluates the lateral collateral ligament. To perform this test, place the knee in thirty degrees of flexion. While stabilizing the knee, adduct the ankle. If the knee joint adducts greater than normal (compare with the uninjured leg), the test is positive. You should notice gapping on the outer side of the knee joint. Many times a "clunk" will be felt if the lateral collateral ligament is injured or torn. This is indicative of a lateral collateral ligament tear.

If you have injured your knee, you may benefit from physical therapy to help you regain normal mobility in the joint. Your PT may perform knee special tests to assess the ligaments around your knee. If your PT suspects a significant ligament tear around your knee, he or she may recommend you check in with an orthopedic surgeon to fully assess your condition.

Edited by Brett Sears, PT.

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