If You Have a Knee Injury

These are the same tests that an orthopedic surgeon, athletic trainer, or physical therapist will often perform before recommending an MRI.

They are called special tests, and they help us determine whether there may be a significant ligament injury that requires further imaging.

Let’s walk through the four main ligaments of the knee and how we assess each one.

1. ACL (Anterior Cruciate Ligament)

The ACL is the injury that most people are worried about, but it is also one of the more straightforward ligaments to test.

The primary test I use is the LACHMAN TEST. In this test, the patient lies on their back with the knee bent to about 30 degrees. The examiner stabilizes the thigh and gently pulls the shin forward.

A positive test occurs when there is more movement, or laxity, in the injured knee compared to the non-injured side.

This is the same test you often see athletic trainers perform on the field when an athlete goes down with a knee injury.

Another test for the ACL is the PIVOT SHIFT TEST. In this test, the knee is moved through a bending and straightening motion while applying a slight inward force. A positive result is a noticeable “clunk” as the knee straightens, which suggests instability.

I will link videos here demonstrating both of these tests.

2. MCL (Medial Collateral Ligament)

For the MCL, the patient lies on their back with the leg straight.

The examiner holds the ankle and applies an inward force at the knee, stressing the inside of the joint.

A positive VALGUS TEST is increased looseness or pain along the inside of the knee compared to the opposite side.

I will link a video here demonstrating this test.

3. LCL (Lateral Collateral Ligament)

The LCL test is very similar to the MCL test, but the force is applied in the opposite direction and is called the VARUS TEST. 

The examiner again stabilizes the ankle, but this time pushes the knee outward, stressing the outside of the joint.

A positive test is increased laxity or discomfort on the outer side of the knee compared to the non injured side.

I will link a video here demonstrating this as well.

4. PCL (Posterior Cruciate Ligament)

The PCL is also relatively straightforward to assess.

One common test is the SAG SIGN. The patient lies on their back with both the hip and knee bent to 90 degrees. From this position, we look to see if the shin drops or “sags” backward compared to the other side.

Another test is the POSTERIOR DRAWER TEST. With the foot flat on the table and the knee bent, the examiner pushes the shin backward.

A positive test is increased backward movement of the shin compared to the non injured side.

I will link a video here demonstrating these tests.

These four ligaments are the primary structures we assess when determining whether someone may need an MRI after a knee injury.

While these tests are very useful, they are just one piece of the full evaluation. We also consider how the injury happened, the level of swelling, and how the knee is functioning overall.

We could also dive into testing for the meniscus, but we will save that for next week.

If you’d like to learn more about knee injuries, I’d love to speak with you over a free phone consultation.

- Dr. Kutsche