What is Anterior drawer test of the knee?
The anterior drawer test is a physical examination performed by the doctors for testing the stability of anterior cruciate ligament (ACL) of the knee.
Doctors generally use this test, images, and other tests, to determine if you’ve sprained or torn your ACL. (Sprain is defined as a tear to a ligament).
The ACL is a crucial ligament in your knee. Therefore, the ACL ligament runs diagonally in the middle of your knee. The ligament prevents your shin bone (tibia) from sliding out in front of your femur, and It also prevents hyperextension of your knee.
Meanwhile, an injury such as a sprain in your ACL may cause significant knee instability. And prevents you from engaging in high-level sports activities that include starting, stopping, and running.
Physical examination Technique
- You should lie in a relaxed supine position.
- Your hip should be flexed to 45 degrees and your knee should be flexed to 90 degrees. And your feet should be lying flat on the table.
- The examiner should sit on your involved foot to stabilize it’s position while grasping your lower knee joint with both hands.
- Examiner should grasp your knee with her thumb in the front of your knee and her fingers behind your knee as shown in the diagram below. Examiner’s fingers should be well tucked up into the flexed part of your knee. And her thumbs should be on the superio-anterior aspect of the tibia.
- Now examiner will gently pull your shin bone (tibia) forward while observing how far the tibia moves.
- Repeat the test on your other leg (healthy leg), and compare the degree of forwarding movement of the tibia.
When the test is positive
The test is positive when your tibia is displaced more than 5 mm or more than the uninvolved side. This will give an indication to the examiner that your ACL is not working correctly, either you may have sprained or torn your ACL ligament.
If your physician performs the Anterior Drawer Test and it’s positive, they could suspect an ACL tear and do other tests to verify it.
A thorough and complete knee exam could detect ACL injury in an estimated 80 percent of cases. An anterior drawer test can be one part of these knee examinations. The sensitivity and specificity of an anterior drawer test seem to be better for chronic conditions.
The anterior drawer test has a sensitivity of 92% and a specificity of 91% in chronic conditions, as demonstrated by a meta-analysis accomplished by Benjaminse et al. from the calendar year 2006. In comparison, the evaluation performs way more insufficient in acute conditions as the test has a sensitivity of 49% and a specificity of 58% in acute conditions.
Other tests of ACL injury
As if the anterior drawer test turns out to be positive, doctors could suspect an ACL tear and perform other tests to confirm an ACL tear.
Other tests include –
Pivot shift test
To perform this test you will have to lie in a supine position. After that the examiner will put your leg into internal rotation by one hand, and from the other hand, the examiner will apply the valgus stress and will take your knee from a position of full extension up into the flexion. If the patient feels clunking, disconcerting feeling, then there is suspicion of an ACL tear.
Lachman test is another physical examination that doctors may use to assess the integrity of the ACL. The examiner will bring your leg into 30 degrees of flexion and will slightly externally rotate your leg. And after that, the examiner will put one hand behind your tibia and the other hand on the patient’s thigh. However, the examiner’s thumb must be on the tibial tuberosity. Now examiner will pull your tibia anteriorly. If the test is positive, the damaged ligament will feel soft or mushy to the examiner.
Generally, for the confirmation of an ACL tear, Doctors usually order MRI as it is considered a gold standard test for the confirmation of an ACL tear. The MRI displays soft tissue structures such as ligaments and muscles. Your ACL (along with other ligaments) can be easily visualised, and the images will probably demonstrate the condition of the ligament.
If you have sprained your ACL, then the anterior drawer test can help you determine if you have torn your ACL. Doctors will use it with the other tests for the confirmation of an ACL tear.
After performing all the tests and finally confirming an ACL tear, your doctor will recommend the best treatment. Various treatment options for an ACL tear include knee bracing, medication, physical therapy, and ACL repair surgery.
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