The anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial collateral ligament (MCL), and lateral collateral ligament (LCL) all stabilize the knee in a different direction. A knee ligament test that reveals compromised stability in a specific direction can, therefore, help identify which ligament is affected (if any).
Knee ligament tests can be performed in a medical office without any special equipment. Based on their outcome and a review of your medical history, your healthcare provider may order imaging tests to support the findings and determine how serious the injury is.
This article walks you through how each knee ligament test is done and what it can reveal.
This gauges the integrity of your anterior cruciate ligament (ACL), which prevents the forward slippage of your shin bone underneath your thigh bone.
How It’s Done: The test is performed while you are lying on your back with your knee bent at a 90-degree angle and your foot placed flatly on the table.
The healthcare provider takes hold of your lower leg just behind the knee and gently tugs your leg forward.
What Results Suggest: Excessive motion of your tibia beneath the femur suggests that your ACL may be torn.
As with the anterior drawer test, this is done to assess whether the movement of the tibia in relation to the femur is normal or not.
How It’s Done: The test is performed while you are lying with your back with your knee bent at a 90-degree angle and tilted outward at a 45-degree angle. Your foot is placed flat on the table.
The healthcare provider takes hold of the front of the lower leg just below the knee and exerts steady pressure against it.
What Results Suggest: If the tibia moves backward beyond what is normal, it suggests a PCL tear or injury.
The MCL stabilizes the inner knee and prevents it from splaying too far inward. It also guards it against impact from the outside of the knee.
How It’s Done: The test is performed while you are on your back with your knee bent at a 30-degree angle. A bolster may be placed under your knee to place it in an optimal position.
Some healthcare providers perform the valgus stress test with the knee straight and your leg placed flat on the table.
The healthcare provider grasps your ankle with one hand and your outer thigh with the other. They then exert gentle but forceful pressure, tugging the ankle outward.
What Results Suggest: An MCL tear is suggested if the knee gaps on the inner portion of the joint more than what is normal (compared to the other knee). In some cases, an audible “clunk” may be heard.
This ligament stabilizes the outer knee and prevents it from splaying too far outward. It also protects it against impact from the inside of your knee.
The purpose of the test is to assess whether the LCL is fully intact by checking for any gaps between the tibia and femur on the outer side of the knee joint.
How It’s Done: Like the valgus stress test, this test is performed while you are on your back with your knee bent at a 30-degree angle. A bolster may be placed under your knee for support.
The valgus stress test can also be performed with your knee straight and your leg placed flat on the table.
The healthcare provider grasps your ankle with one hand and places the other on the inner side of your knee. They then exert forceful but gentle pressure, tugging the ankle inward.
What Results Suggest: If the knee gaps on the outer portion of the knee joint more than what is normal, this would suggest an LCL tear. An audible “clunk” may also be heard.
