Clarke Test (Patellar Grind Test): How to Assess Anterior Knee Pain

Anterior knee pain — the kind that shows up going up or down stairs, during deep squats, or after sitting for a long time — is one of the most common complaints in any physiotherapy or training setting. The Clarke test, also known as the patellar grind test, is one of the classic maneuvers for exploring whether that pain has a patellofemoral origin.

What does this test measure?

The Clarke test assesses pain when the patella is compressed against the femoral trochlear groove while the quadriceps contracts, simulating the friction that occurs at the patellofemoral joint during active movement. A positive result points toward retropatellar cartilage issues (chondromalacia patellae) or patellofemoral pain syndrome in general.

Equipment needed

• Treatment table
• No additional equipment

Protocol

1. The patient lies supine, with the knee in full extension and relaxed
2. Place the web of your hand (the "V" between thumb and index finger) over the superior pole of the patella, applying light downward and caudal pressure
3. Ask the patient to contract the quadriceps (as if pushing the knee down into the table) while you maintain pressure on the patella
4. Watch for pain during the contraction, and whether the patient "gives up" the contraction due to discomfort (this is sometimes considered part of the sign)

Common mistakes

• Applying too much pressure, which can cause pain in anyone (pressure should be moderate, not aggressive)
• Not asking for a genuine active quadriceps contraction (the test loses its meaning if the knee stays passive)
• Confusing normal mild discomfort with a true positive pain sign

How to interpret the results

Result	Interpretation
Clear retropatellar pain during contraction, patient "gives up" the contraction	Positive — suggests patellofemoral pain syndrome / chondromalacia patellae
Mild discomfort, no clear pain and contraction maintained	Inconclusive — assess alongside the rest of the exam
No pain, full and sustained contraction	Negative

The Clarke test has limited specificity (it can come back positive in healthy knees if too much pressure is applied), so it should be interpreted alongside the clinical picture (pain on stairs, squatting, prolonged sitting) and not in isolation.

Relationship with other tests

The Clarke test is often combined with:

• Patellar apprehension test — to assess patellar instability alongside the friction-related pain component
• Single-leg hop test for ACL — useful for assessing functional tolerance of anterior knee pain under load

Track the progression of anterior knee pain

Patellofemoral pain usually responds well to progressive strengthening programs (quadriceps, glutes), but it needs time and follow-up to confirm improvement. In Movalytics you can log the Clarke test result at each assessment alongside a pain scale during functional activities (squatting, stairs), and track whether the trend is improving as the program progresses.

Frequently asked questions

Is the Clarke test painful for everyone? With excessive pressure it can cause discomfort even in healthy knees, so it's important to apply moderate pressure and compare with the opposite knee. Does a positive result mean there's cartilage damage? It suggests a patellofemoral friction/compression component, but it doesn't by itself confirm the degree of cartilage damage; that would require imaging (MRI) if needed. What's typically recommended if the test is positive? Usually quadriceps strengthening (especially the vastus medialis) and glute work, training load management, and a review of technique in exercises like squats or lunges.