Overview
The trapeziometacarpal (CMC) joint sits at the base of the thumb, where the thumb metacarpal meets the trapezium bone of the wrist. Unlike most joints, it moves in multiple planes to allow the thumb to rotate and oppose the fingers - the motion that makes grip and pinch possible. That mobility comes at a cost: the joint surfaces are under high load during everyday tasks, and the cartilage that cushions them can wear down over time. When it does, the condition is called trapeziometacarpal osteoarthritis, or rhizarthrosis.
As the cartilage thins, the joint space narrows and the bones begin to contact each other directly on pinch and grip. Pain at the base of the thumb is the result. In more advanced cases, the joint can sublux - the thumb metacarpal drifts radially, producing the visible prominence at the base of the thumb that is characteristic of late-stage disease. The condition typically progresses through four radiographic stages (Eaton I–IV); surgical options become relevant from stage II onwards when conservative care has failed.
Symptoms
- Pain at the base of the thumb on grip and pinch activities
- Difficulty opening jars, turning keys, or buttoning clothing
- A weak or unstable feeling at the thumb base
- Visible prominence or "shouldering" at the base of the thumb
- Stiffness in the morning that eases with movement
Who's affected
- Adults over 40, more commonly women
- Patients with a history of repetitive thumb use (manual trades, musicians)
- Patients with previous thumb-base trauma or instability
- Patients with generalised osteoarthritis affecting other joints
Diagnosis
Diagnosis is primarily clinical. The grind test - axial compression combined with circumduction of the thumb metacarpal - reproduces pain at the CMC joint and is the most reliable provocation sign. Tenderness on direct palpation of the joint and pain on tip-to-tip pinch are also characteristic findings.
Plain X-rays (posteroanterior and stress views) confirm the diagnosis and stage the disease. Eaton staging guides treatment: stage I shows a normal or slightly widened joint space; stages II and III show progressive joint-space narrowing and osteophyte formation; stage IV shows severe arthritic destruction. Advanced imaging (MRI or CT) is rarely required for straightforward rhizarthrosis but may be requested in atypical presentations or when surgical planning requires detailed anatomical assessment.
Treatment options
Conservative care
Splinting, anti-inflammatories, hand therapy, activity modification - first-line for most patients.
PRGF infiltration (private-pay)
Autologous Plasma Rich in Growth Factors with Endoret® PRGF - see the PRGF / PRP injection procedure page.
CMC arthroplasty (GESY-covered)
Surgical replacement of the trapeziometacarpal joint with the Touch® CMC Prosthesis - see the CMC arthroplasty procedure page.
Devices used
Procedures
When to see a surgeon
Most patients benefit from a surgical consultation once conservative care - splinting, anti-inflammatories, and hand therapy - has been tried for three to six months without adequate relief. Earlier referral is reasonable if pain is disrupting sleep or work, if pinch strength is significantly reduced, or if the disease is radiographically advanced at presentation. The consultation does not commit you to surgery: a hand surgeon can confirm the diagnosis, stage the disease, and advise on whether to continue conservative care or plan for CMC arthroplasty.
GESY coverage in Cyprus
CMC arthroplasty with the Touch® CMC Prosthesis is GESY-covered in Cyprus. When performed by a participating hand surgeon at a GESY-contracted hospital, the device cost is included in the hospital reimbursement; patients are not billed separately for the implant.
PRGF infiltration (Endoret® PRGF) is not GESY-reimbursable. Regenerative medicine sits in the private-care tier in Cyprus and is delivered through private clinics on a self-pay basis.
