Patellar grind test (Clarke`s Sign)

The Patellar Grind Test, also known as Clarke’s Sign, is used to identify patellofemoral pain syndrome (PFPS), chondromalacia patellae, or patellofemoral degenerative joint disease (DJD). A positive test indicates pain in the patellofemoral joint during quadriceps activation【1】.

Execution

Patient position:

• The patient lies supine or in long sitting with the knee fully extended.

Test procedure:

1. The clinician places the web space of the hand just superior to the patella.

2. Downward pressure is applied to prevent superior glide of the patella.

3. The patient is asked to contract the quadriceps gradually against resistance.

4. The clinician observes for reproduction of pain.

Interpretation:

• Positive test: Retropatellar pain, and the patient is unable to maintain quadriceps contraction without discomfort.

• Negative test: Quadriceps contraction without pain or discomfort.

Alternative Method (Rieder Modification)

The clinician presses directly downward on the patella while the patient contracts the quadriceps. Pain and inability to sustain contraction indicate patellofemoral pain syndrome【2】.

Clinical Considerations

• The applied pressure must be controlled, as excessive force may lead to false positives, even in healthy individuals.

• The test should be repeated multiple times with gradually increasing pressure and compared to the contralateral side.

• Performing the test at different knee angles (30°, 60°, 90°, and full extension) can help assess different areas of the patellofemoral joint【2】.

Evidence and Reliability

• The test is grounded in patellofemoral biomechanics but lacks strong validation in research.

• Low specificity: Many individuals may report pain even without PFPS【3】.

• Should not be used as a standalone diagnostic tool, but rather in combination with other clinical assessments【4】.

Diagnostic Value

• Positive likelihood ratio (LR+): 1.94

• Negative likelihood ratio (LR–): 0.69【2】

Conclusion

Clarke’s Test (Patellar Grind Test) is simple to perform but has limited diagnostic value when used alone. It can, however, serve as part of a broader assessment for patients with suspected patellofemoral pain syndrome.

Sources:

1. Baxter R. Pocket Guide to Musculoskeletal Assessment, 2nd edition. Copyright 2003, Elsevier Science (USA).

2. Magee DJ: Orthopedic Physical Assessment, 5th ed. Philadelphia, WB Saunders, 2008.

3. Magee DJ: Orthopedic Physical Assessment, 4th ed. Philadelphia, WB Saunders, 2002.

4. Fredericson M, Yoon K. Physical Examination and Patellofemoral Pain Syndrome. Am J Phys Med Rehabil. 2006 Mar;85(3):234-43.