How to spot and treat Thumb Base Arthritis (CMC Joint Osteoarthritis)

The carpometacarpal (CMC) joint of the thumb (also called the trapeziometacarpal joint) is highly mobile and is subjected to considerable forces during pinch, grip, and dexterous tasks. This combination makes it vulnerable to degenerative changes, overuse, trauma, and instability. When conservative measures fail to deliver adequate pain relief or function, surgical intervention becomes a consideration.

Understanding when surgery is appropriate, which surgical options exist, and what outcomes to expect is essential for both patients and clinicians. In the UK, the British Society for Surgery of the Hand (BSSH) has produced the BEST guideline on thumb base osteoarthritis, which provides structured recommendations.

Below, we review:

The pathology, symptoms, and conservative management
Indicators and criteria for proceeding to surgery
The main surgical options, risks, and expected outcomes
Key counselling points and follow-up considerations

Pathology, Symptoms & Conservative Management

Pathology & Biomechanics

The thumb CMC joint sits between the base of the first metacarpal and the trapezium bone of the wrist. It allows flexion/extension, abduction/adduction, and a degree of axial rotation (opposition). Over time, or after trauma, cartilage degeneration, subchondral sclerosis, osteophyte formation, and joint subluxation may develop, leading to osteoarthritis.

Because the joint must both bear load and allow mobility, degeneration frequently ends up producing pain, instability, and functional limitation. In more advanced cases, the joint’s alignment may shift, and secondary changes (e.g., in adjacent joints) may occur.

Clinical Presentation & Diagnosis

Typical symptoms include:

Pain at the base of the thumb (often worse during pinch or grip activities, e.g. opening jars, turning keys)
Tenderness on palpation of the CMC joint
Swelling, crepitus, or bony prominence at the base of the thumb (“bossing”)
Weakness of pinch, grip fatigue
Loss of range of motion, stiffness
In advanced cases, deformity (a “zigzag” thumb posture) due to metacarpophalangeal hyperextension compensating for CMC collapse

On examination, doctors often test for pain with load across the joint, “grind test” (axial compression + rotation), and assess stability. Plain radiographs are standard (AP, lateral, oblique views) to grade the severity of arthritic change, subluxation, and joint space narrowing.

Where there is ambiguity about the involvement of adjacent joints (e.g. the scaphotrapeziotrapezoidal joint, STT), further imaging may be necessary.

Conservative Management (First Line)

All patients should undergo non‑surgical management first, unless the condition is extreme.

According to the BSSH BEST guideline, a stepwise multimodal approach is recommended. Common measures include:

Education and activity modification (avoiding aggravating tasks)
Analgesics / NSAIDs (or topical agents)
Splinting / orthoses (thumb spica or CMC support) to offload the joint
Hand therapy: strengthening of thenar muscles, joint protection techniques, exercises
Intra‑articular corticosteroid injections for temporary relief in recalcitrant cases

According to the BSSH BEST guidance, if symptoms persist despite “a comprehensive non-invasive management package” (splinting, therapy, analgesics), then surgical options can be considered.

However, it is important to emphasise that conservative measures may not completely remove all symptoms but aim to improve pain control, maintain function, and delay or avoid surgery.

When Is Surgery the Right Option?

Moving to surgery is a significant decision. Not every patient with thumb CMC osteoarthritis is a surgical candidate, and not all surgical techniques are appropriate for everyone. The decision should balance symptom severity, functional limitation, patient expectations, comorbidities, and risk vs benefit.

Here are key indications, contraindications, and decision factors:

Indications for Surgery

Failure of adequate conservative therapy
If pain, functional limitation, and reduction in quality of life persist despite a reasonable trial of nonoperative methods (often many months)
Daily activities severely impaired
If tasks such as grasping, pinching, opening jars, turning keys, or personal tasks are markedly restricted, despite nonoperative measures.
Progressive disease and structural collapse
Radiographic progression, subluxation, joint instability or deformity may push the balance toward surgical intervention if symptomatic.
Patient expectations and tolerances
Some patients may accept residual symptoms and adaptation; others may prefer more definitive surgical correction.
Good surgical candidacy
Patients who are medically fit, with realistic expectations, and able to engage with postoperative rehabilitation.

The BSSH BEST guideline suggests that if symptoms fail to resolve after non-invasive management, surgery should be considered.

Surgical Options: Techniques, Pros & Cons, Evidence

Once surgery is judged to be the right option, surgeons may choose among several techniques. The most common ones include:

Trapeziectomy (excision of the trapezium)
Trapeziectomy + Ligament Reconstruction / Tendon Interposition (LRTI)
Arthrodesis (fusion) of the CMC joint
Joint replacement / arthroplasty (total CMC prosthesis, hemiarthroplasty, or implant devices)

Each has advantages, drawbacks, and evidence.

Trapeziectomy (Simple Excision)

This is the “classic” and still most commonly used operation. It involves removing the trapezium bone to eliminate the arthritic articulation. Some surgeons may leave the gap (simple resection), while others may stabilise the thumb metacarpal using soft tissue interposition or tendon grafts.

Pros:

Reliable pain relief in many patients
Avoids putting a prosthesis or rigid construct
Good long-term results in many series
Less risk of implant-related complications (loosening, wear)

Cons:

Potential instability or shortening of the thumb
Loss of pinch strength compared to an ideal prosthesis
Prolonged rehabilitation and adaptation

The BSSH BEST guideline notes that additional procedures (interposition or ligament reconstruction) do not appear to confer major benefit over simple excision (trapeziectomy alone) in their systematic evaluation.

Trapeziectomy + Ligament Reconstruction / Tendon Interposition (LRTI)

To address concerns about instability or metacarpal collapse, surgeons often pair trapeziectomy with a soft tissue procedure — e.g. using a strip of the flexor carpi radialis (FCR) tendon to reconstruct ligaments or interpose tissue in the gap (thus stabilising the thumb).

Pros:

Additional stabilisation may better preserve pinch strength
Less risk of metacarpal subluxation or collapse
Many surgeons believe it yields a more stable thumb base

Cons:

More surgical complexity
Donor tendon morbidity
Slightly longer recovery
Mixed evidence on superiority over simple trapeziectomy (BSSH BEST suggests limited added benefit)

To explore differences in stability between a trapeziometacarpal prosthesis and trapeziectomy/ligamentoplasty, please see the clinical paper linked below:
Hyperextension MP.pdf

CMC Joint Fusion (Arthrodesis)

Fusion of the CMC joint is less common and is typically reserved for younger patients or in specific circumstances. By fusing the joint, pain is eliminated but mobility is sacrificed.

Pros:

Stable, pain-free base
May preserve grip strength better than excision in some patients

Cons:

Loss of mobility of the CMC (no motion at that joint)
Increased stresses on adjacent joints (e.g. MCP, wrist)
Risk of non-union, hardware failure

Because of the mobility lost, fusion is used selectively (e.g. high demand or where implant options are not favourable).

Joint Replacement / Arthroplasty

This involves replacing the articulating surfaces with a prosthesis (either full or partial). Several designs exist: total CMC implants, hemiarthroplasty, or synthetic cartilage implants (e.g. the MAIA implant) in more recent practice.

Pros:

Potential for better preservation of motion
Theoretically improved function and biomechanical behaviour
Faster return to certain tasks in some series

Cons:

Risk of implant loosening, subsidence, failure, dislocation over time
Revision surgery may be required
Higher cost, greater technical demand
Long-term durability is still under study

The MAIA implant could be an excellent option given its claimed advantages:

Restores natural thumb movement using a dual-mobility ball-and-socket design.
Improves pain, function, and grip/pinch strength compared with baseline (and often compared with trapeziectomy).
Provides an anatomical fit through multiple cup, stem and neck size options.
Offers stable long-term fixation via porous, cementless components and titanium options for metal-sensitive patients.
Aims for faster recovery and an earlier return to hand function than traditional alternatives.

To find out more about MAIA, please visit our website: MAIA – CMCJ Replacement – LEDA.

One clinical series of cemented total trapeziometacarpal implants in advanced disease (Eaton stage III/IV) showed good outcomes at average 59 months: most patients were pain-free; average pinch strength ~85% of the unaffected side; minimal loosening in follow-up.

In the UK, when using implants like MAIA, aftercare protocols typically involve cast / splint immobilisation initially, followed by rehabilitation over weeks to months.

Trapeziectomy remains a gold standard in many UK services, partly because of its reliability and lower risk of long-term implant complications; the BEST guideline acknowledges prosthetic techniques but highlights the need for balanced decision-making.

Expected Outcomes, Risks & Counselling

Outcomes & Time Course

Pain relief is the primary target. Most patients notice improvement within a few months; full recovery may take 6 to 12 months.
Range of motion generally improves, but residual stiffness may persist.
Pinch strength often recovers, though rarely to full pre‑disease levels, especially in heavier-demand tasks.
Implant-based surgeries carry some probability of revision over time; prosthetic loosening or failure may appear years later.

Risks & Complications

Common risks to discuss include:

Infection, wound healing problems
Nerve irritation or injury (sensory branches near the thumb base)
Tendon injury
Persistent pain or lack of relief
Implant failure, loosening, dislocation (for arthroplasty)
Complex Regional Pain Syndrome (CRPS)
Non-union (if fusion attempted)
Loss of joint motion (especially with fusion)
Donor tendon morbidity (in LRTI)

Shared Decision Counselling

To help patients decide, the clinician should:

Explain the prospects vs risks of each surgical option, in light of their age, activity level, imaging findings, and expectations
Clarify that surgery is not guaranteed to restore full strength or eliminate all symptoms, but aims to improve pain and function
Discuss the rehabilitation commitment and timeline (often many months)
Review alternative strategies and risks of delaying surgery (progressive joint damage, possible worsening of symptoms)
Emphasise the importance of selecting a surgeon experienced in thumb CMC procedures and in long‑term follow-up

Practical Algorithm: From Diagnosis to Surgical Decision

Here is a simplified decision pathway:

Diagnosis & grading
- Confirm CMC joint involvement, assess radiographs (stage disease), check adjacent joint involvement.
Trial of nonoperative treatment (3–12 months)
- Splints, therapy, activity modification, analgesics, injections
Reassess symptom severity & function
- If acceptable, continue nonoperative care
- If inadequate, consider surgical referral
Patient evaluation & counselling
- Medical fitness, expectations, hand dominance, occupation
Choose appropriate surgical technique
- For most patients, trapeziectomy (with or without LRTI)
- In select patients, arthroplasty/fusion options
Surgery + postoperative care
- Immobilisation, hand therapy, phased rehabilitation
Monitoring outcomes and complications
- Radiographic follow-up, functional scores, grip/pinch strength

The BSSH BEST guideline endorses a stepwise approach, whereby surgery is reserved for those who do not respond to conservative treatment.

Summary & Recommendations

Thumb CMC (trapeziometacarpal) osteoarthritis is common and painful, often requiring a structured management plan.
Conservative treatments (splints, therapy, analgesics, injections) are first-line and should be given a fair trial.
Surgery becomes an option when symptoms remain debilitating, functional limitation is significant, and imaging supports structural change.
Among surgical options, trapeziectomy (with or without ligament reconstruction / tendon interposition) remains the mainstay in many UK practices, with a good track record of pain relief and acceptable outcomes.
Arthroplasty / joint replacement is a promising alternative in selected patients, though long-term durability and revision risk must be weighed.
Fusion is reserved for specific scenarios and is less favoured due to loss of motion.
Outcomes tend to improve gradually over months; patients should be counselled about realistic expectations, recovery time, and the risk of residual limitations or complications.
Shared decision-making, skilled surgical technique, and dedicated postoperative rehabilitation are all critical to maximise results.