Patellar Grind Test (Clarke's Sign): Checking Kneecap Pain
Updated: 3 days ago
Written and medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: November 2026 · How we review
Quick Answer
The patellar grind test, also called Clarke's sign, is a knee exam that checks whether pain around the kneecap comes from cartilage problems. The provider presses on your kneecap and asks you to tighten your thigh muscle. Pain or grinding is a positive result. The test can be positive in healthy knees, so it's combined with other exams.
What the research says
The test alone isn't very accurate: in 106 people having knee arthroscopy, the Clarke sign detected cartilage softening under the kneecap with only 39% sensitivity and 67% specificity, leading the researchers to question its routine use (Doberstein ST et al., J Athl Train, 2008) [2]
No single exam test is definitive: a systematic review of clinical tests for patellofemoral pain found none had strong enough accuracy on its own; the patellar tilt test and squatting showed the most promise (Nunes GS et al., Phys Ther Sport, 2013) [3]
Key takeaways
A quick exam for pain around the kneecap.
Checks for cartilage wear under the patella and patellofemoral pain.
Positive means pain, grinding or trouble holding the thigh tight.
Healthy knees can test positive.
Usually combined with other tests and imaging.
What does the test check?
The test looks at the cartilage behind the kneecap.
The patella (kneecap) glides over the front of the thigh bone, protected by cartilage. The grind test helps tell whether knee pain comes from that cartilage. Sources: [1]
Chondromalacia patellae: softening and breakdown of the cartilage under the kneecap.
Patellofemoral pain syndrome: also called runner's knee.
It can also help rule out pes anserine bursitis and knee osteoarthritis. Sources: [1]
Knee pain like this is common in athletes and active people, often from tight thigh muscles or repeated running and jumping. Sources: [1]
How is the test done?
The test takes just a minute.
You lie on an exam table with your legs straight and thigh muscles relaxed.
Your provider places the web of their hand over the top of your kneecap.
They press the kneecap down or inward while you tighten your thigh (quadriceps) muscle.
The other knee is usually tested too, sometimes at different knee angles. Sources: [1]
No preparation is needed. Athletic trainers, orthopedists, physical therapists and primary care providers can perform it. Sources: [1]
Understanding your results
Results are known right away.
Positive: a grinding noise, pain or being unable to keep your thigh muscle tight under pressure; this may mean the cartilage is wearing down.
Negative: no problems during the test. Sources: [1]
Because the test can be positive in healthy knees and can miss problems, it's only one part of the exam. Sources: [1, 2, 3]
What happens next?
Your provider may order a knee X-ray, CT or MRI, blood tests for conditions like gout or rheumatoid arthritis, or knee arthroscopy to look inside the joint. Sources: [1]
Conclusion
The patellar grind test is a simple first step in sorting out kneecap pain. Because its accuracy is limited, your provider will use it alongside your history, other exam tests and imaging.
Keep learning: read about patellofemoral pain syndrome and the kneecap.
Frequently asked questions
What is the patellar grind test?
A knee exam that checks for cartilage problems under the kneecap.
What is Clarke's sign?
Another name for the patellar grind test.
What does a positive test mean?
Pain, grinding or weakness that may suggest cartilage wear.
Can a healthy knee test positive?
Yes.
Does the test hurt?
It may cause pain if there's a problem under the kneecap.
Do I need to prepare?
No.
Who performs it?
Athletic trainers, orthopedists, physical therapists or primary care providers.
What tests might come next?
X-ray, MRI, CT, blood tests or arthroscopy.
What conditions can it suggest?
Chondromalacia patellae and patellofemoral pain syndrome.
Is it accurate?
Not very on its own, so it's combined with other tests.
Related Reading
Spurling Test: Checking for a Pinched Nerve in the Neck explains the neck exam test for a pinched nerve.
Patellofemoral Pain Syndrome (PFPS): Symptoms, Causes, and Recovery the knee pain the test helps evaluate.
Patella: Kneecap Anatomy, Function, Injuries and Care how the kneecap works.
What is Knee Osteoarthritis? a condition the test can help rule out.
Knee Arthroscopy: A Minimally Invasive Approach to Joint Health a scope exam of the knee.
Knee X-Ray: Why It's Done, What It Shows and What to Expect imaging often done next.
References
Cleveland Clinic. Patellar Grind Test/Clarke's Sign for Patellofemoral Pain. Cleveland Clinic. Last updated February 14, 2022. https://my.clevelandclinic.org/health/diagnostics/22428-patellar-grind-test
Doberstein ST, Romeyn RL, Reineke DM. The diagnostic value of the Clarke sign in assessing chondromalacia patella. J Athl Train. 2008;43(2):190-196. PMID 18345345. https://doi.org/10.4085/1062-6050-43.2.190
Nunes GS, Stapait EL, Kirsten MH, et al. Clinical test for diagnosis of patellofemoral pain syndrome: systematic review with meta-analysis. Phys Ther Sport. 2013;14(1):54-59. PMID 23232069. https://doi.org/10.1016/j.ptsp.2012.11.003
Medical disclaimer
This article is for general education only and does not replace advice from a qualified healthcare professional. Talk to your doctor about your own diagnosis and treatment, and seek emergency care right away for severe or sudden symptoms.
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