Diagnosing Rhizarthrosis: Clinical Tests & Imaging Guide
Suspect you have thumb arthritis? Diagnosis starts with a clinical examination and is confirmed with imaging. Understanding the diagnostic process helps you prepare for your appointment and ask the right questions.
This guide covers the clinical tests, imaging techniques, and staging systems used to diagnose and classify rhizarthrosis.
Clinical Examination
Your doctor will perform several hands-on tests:
- Grind Test (CMC compression test) — The examiner pushes and rotates the thumb metacarpal into the trapezium. Pain and crepitus (grinding sensation) suggest arthritis.
- Shear Test — Side-to-side pressure at the CMC joint to assess instability
- Pinch strength testing — Reduced pinch strength compared to the opposite hand is a common finding
- Observation — Looking for swelling at the thumb base, Z-deformity, and muscle wasting (thenar atrophy)
Imaging & Staging
Standard imaging for rhizarthrosis includes:
- X-ray (Robert view) — A specialised thumb X-ray showing the CMC joint in true AP projection
- Stress X-rays — Taken while applying force to reveal joint instability
- CT scan — Sometimes used for surgical planning in complex cases
- MRI/Ultrasound — Occasionally used to assess soft tissue damage or early disease
The Eaton-Littler classification (stages I–IV) is the standard staging system used worldwide to grade rhizarthrosis severity and guide treatment decisions.
Research & Articles
Browse all 3 evidence-based articles in this category:
Rhizarthrosis vs De Quervain’s: How to Tell the Difference
Key Takeaways When your thumb hurts near the wrist, it can be confusing to figure out what is going on. […]
Thumb Pain at the Base: What It Means and When to See a Doctor
Key Takeaways If you have noticed a deep, aching pain right where your thumb meets your wrist, you are not […]
Is My Finger Injury Being Diagnosed Correctly?
When you hurt your finger and the tip droops down, doctors need to figure out exactly what happened inside. This […]
Frequently Asked Questions
What is the Grind Test?
The Grind Test (or CMC compression test) is the most common clinical test for rhizarthrosis. Your doctor holds your thumb and pushes it firmly into the base while rotating it. If this reproduces your pain and you feel a grinding sensation, the test is positive.
Do I need an MRI for thumb arthritis?
Usually not. Standard X-rays (especially the Robert view) are sufficient to diagnose and stage rhizarthrosis. MRI is rarely needed unless the diagnosis is unclear or your doctor suspects additional soft tissue problems.
What do the Eaton stages mean for my treatment?
Stage I–II: Usually managed with conservative treatment (splints, therapy, injections). Stage III: Surgery may be recommended if conservative measures fail. Stage IV: Surgery is typically recommended, with trapeziectomy being the most common procedure.
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Medical Disclaimer: This information is based on published scientific research and is intended for educational purposes only. It does not replace professional medical advice. Always consult your doctor or hand surgeon for personalised treatment recommendations.