What is the CMC Grind Test used for?

Diagnosing Osteoarthritis of the Thumb Carpometacarpal (CMC) Joint.

How do you perform the CMC Grind Test?

Position: Examiner grips the patient's thumb metacarpal bone.Action: Apply an axial compressive force while rotating the thumb (grinding motion) against the trapezium.

What is a positive result for the CMC Grind Test?

Positive Test: Sudden sharp pain at the CMC joint, often accompanied by crepitus (grinding sound/feeling).Why: This grinds the worn cartilage surfaces together, reproducing arthritis pain.

What is the diagnostic accuracy of the CMC Grind Test?

Sensitivity: 42%Specificity: 80%

CMC Grind Test – Wrist & Hand Special Test

What is it used for?

Diagnosing Osteoarthritis of the Thumb Carpometacarpal (CMC) Joint.

How to Perform

Position: Examiner grips the patient's thumb metacarpal bone.
Action: Apply an axial compressive force while rotating the thumb (grinding motion) against the trapezium.

Interpretation of Results

Positive Test: Sudden sharp pain at the CMC joint, often accompanied by crepitus (grinding sound/feeling).
Why: This grinds the worn cartilage surfaces together, reproducing arthritis pain.

Diagnostic Accuracy

Sensitivity: 42%
Specificity: 80%

Clinical Context & Limitations

The CMC Grind Test should be considered as one component of a comprehensive musculoskeletal assessment. No single special test has perfect diagnostic accuracy; thus, clinical decision-making should integrate test results with patient-reported symptoms, mechanism of injury, functional impairment, and relevant imaging.

Clinicians should be aware of potential false-positive results in patients with pain sensitisation, muscle guarding, or poor relaxation. For the Wrist & Hand region, combining the CMC Grind Test with complementary examination tests significantly improves overall diagnostic confidence.