Patellar Grind Test

What is the patellar grind test?

The patellar grind test is a simple procedure that healthcare professionals use to assess knee pain. It can help determine whether pain around your patella is caused by the breakdown of cartilage. It’s also called Clarke’s sign, Clarke’s test and Zohlen sign.

Your patella is your kneecap, a triangular bone at the front of your knee. It protects your knee joint and connects to muscles in your upper and lower leg. Under your patella is cartilage, which helps your knee move and protects your knee joint.

When is Clarke’s test performed?

Knee pain is common, especially in athletes and other active individuals. If you have pain in or near your patella, Clarke’s sign may help determine the reason.

Sometimes the cause is a breakdown of the cartilage under your kneecap. This is more likely if your knee has unbalanced pulling forces, such as a tight quadriceps muscle. Or it may occur with repetitive stress and pressure on the knee, such as running and jumping.

A positive Clarke’s test can help a healthcare provider tell whether knee pain is caused by cartilage breakdown:

• Chondromalacia patellae, when the tissue (cartilage) under your kneecap softens and breaks down.
• Patellofemoral pain syndrome also called runner’s knee or jumper’s knee.

The test may help healthcare providers rule out other possible causes of knee pain, such as:

• Anterior knee pain (pes anserinus bursitis), inflammation of a fluid-filled sac on the inside of your knee joint.
• Osteoarthritis, or degenerative joint disease.

Who performs the patellar grind test?

Healthcare providers who may perform the test include:

• Athletic trainers.
• Orthopedists (bone and joint specialists).
• Physical therapists.
• Primary care providers.

How does the patellar grind test work?

A healthcare provider will ask you to:

• Lie down on an examination table.
• Extend (straighten) your legs.
• Relax your quadriceps muscles (a group of four muscles in the front of each thigh).

They place one hand on the top of one of your knees, toward your thigh. Their thumb is on the outside of your leg, and their fingers are positioned toward the inside of your leg. The webbing between their thumb and pointer finger stretches over the top of your kneecap.

Then they push the kneecap downward or inward. The healthcare provider will ask you to contract (squeeze) your quad, as if you are trying to extend the knee further.

The healthcare provider will likely perform the test on the other knee, even if your knee problem is only on one side. They may perform the test several times at different knee angles.

What does a positive Clarke’s sign mean?

The test is positive if you experience:

• Grinding noise.
• Inability to contract the quad with pressure on your knee.
• Pain.

A positive test may mean that the cartilage under your patella is wearing down. The test is negative if you don’t experience any issues during the test.

How do I prepare for the patellar grind test?

You don’t have to do anything to prepare for the patellar grind test. It’s a common procedure usually performed in a doctor’s office.

What happens after the patellar grind test?

After the test, the healthcare provider will talk to you about the results and what they might mean. They’ll also tell you whether you should have any other tests.

Is the patellar grind test reliable?

The patellar grind test can be positive (grinding or pain) in patients who have healthy knees. It’s one of many tools a healthcare provider uses to assess knee pain. It usually must be combined with other tests for an accurate, comprehensive diagnosis.

When should I know Clarke’s test results?

You’ll know the results of the patellar grind test immediately. But it may be only one step in assessing knee pain. Your healthcare provider also may recommend:

• Blood tests to measure chemicals in the blood that indicate conditions such as gout or rheumatoid arthritis.
• Knee arthroscopy, a minimally invasive procedure used to examine the knee joint.
• X-ray, CT scan or MRI to take pictures of the knee joint.

A note from Cleveland Clinic

The patellar grind test is a simple procedure used to assess knee pain. It can help a healthcare provider determine whether you have cartilage breakdown under the kneecap. If you have knee pain, talk to a healthcare provider about what tests and treatments you might need.