Thumb base arthritis
Osteoarthritis of the carpometacarpal (CMC) joint at the base of the thumb, causing pain with pinch, grip, and twisting movements. One of the most common sites of hand osteoarthritis, particularly in women over 50.
📊 Symptomatic thumb base osteoarthritis affects around 15% of women and 7% of men over the age of 50. Radiographic changes are present in up to one third of postmenopausal women.
What is thumb base arthritis?
The joint at the base of the thumb, between the trapezium bone and the first metacarpal, is uniquely shaped to allow the thumb to move in many directions and to oppose the fingers. This wide range of movement comes at a price: the joint is heavily loaded with every pinch and grip, and the cartilage that lines it is prone to wear with age. As the cartilage thins, the underlying bone becomes exposed, the joint surfaces grind against each other, and small bony spurs (osteophytes) form around the joint.
The result is pain at the base of the thumb on any pinching or gripping activity, turning a key, opening a jar, holding a phone, doing up buttons. Many patients describe a deep ache that wakes them at night. As the disease progresses the base of the thumb becomes prominent and the thumb may collapse into a "Z-shape" (adduction at the base, hyperextension at the MCP joint).
Despite how much it can hurt, thumb base arthritis can almost always be managed without surgery in the early years. Splinting and a corticosteroid injection often give excellent relief. When the pain is no longer controlled by these measures, surgery, most commonly trapeziectomy, is highly successful, although recovery takes several months.
Common causes
- Age-related cartilage wear, the dominant cause
- Female sex and postmenopausal hormonal changes
- Genetic predisposition (strong family history common)
- Previous fracture involving the joint (Bennett or trapezial fracture)
- Generalised osteoarthritis affecting other joints
- Occupational use involving repetitive thumb gripping or pinching
Who is at risk? Female sex, age over 50, postmenopausal status, and a positive family history are the strongest risk factors. Occupations involving repetitive forceful pinching (seamstresses, dentists, manual workers) may accelerate onset.
Symptoms
Symptoms vary depending on the severity and duration of the condition. Common symptoms include:
- Aching pain at the base of the thumb, worse with use
- Pain on pinching, gripping, turning keys, opening jars
- Weakness of grip and pinch strength
- A grinding or grating sensation in the joint
- A visible prominence at the base of the thumb as the disease progresses
- In late disease: a "Z-shaped" thumb deformity
When to seek help: See your GP or hand specialist if thumb base pain is interfering with daily activities, if it wakes you at night, or if you notice the thumb is becoming weaker or more deformed. Early treatment with a splint and injection can give excellent symptom relief.
How is it diagnosed?
Your hand surgeon will take a detailed history and examine the hand and wrist. The following investigations may be arranged to confirm the diagnosis:
- Clinical examination, tenderness at the base of the thumb
- Grind test, axial compression and rotation reproduces pain
- Crank test, circumduction reproduces grinding
- Plain X-rays, staged using the Eaton-Littler classification (Stage 1-4)
- Assessment of MCP joint hyperextension and Z-deformity
X-ray staging guides treatment but symptoms often correlate poorly with radiographic stage, some patients with advanced X-ray changes have minimal pain, and vice versa. Treatment is guided by symptoms and functional impact rather than X-ray appearance alone.
Treatment pathway
Treatment is tailored to the severity of the condition, your age, activity level, and overall health. Most conditions are treated in a stepwise fashion, starting with the least invasive options.
Splinting and activity modification
A custom-fitted thumb spica splint worn during aggravating activities offloads the joint and reduces pain. Activity modification (using larger grips, adaptive tools) and a graded hand therapy programme improve function. Anti-inflammatory medication can be used for flares.
Corticosteroid injection
A targeted injection into the CMC joint, often performed under ultrasound guidance to ensure accurate placement. Provides excellent relief for several months in most patients. Repeated injections are limited (usually no more than 2-3) but can defer surgery for years in many people.
Trapeziectomy
The trapezium bone is removed entirely, sometimes with a ligament reconstruction or interposition of a piece of tendon to fill the space. The most widely performed operation for thumb base arthritis. Highly successful in relieving pain, but recovery takes several months and grip strength continues to improve for up to a year.
Joint replacement or arthrodesis
Modern thumb base joint replacements give faster recovery and better strength than trapeziectomy in selected patients, although long-term durability data are still emerging. Joint fusion (arthrodesis) is rarely performed and reserved for young, heavy manual workers who prioritise strength over movement.
Recovery
After trapeziectomy the thumb is held in a cast or splint for 4-6 weeks, followed by hand therapy. Most patients are doing well by 3 months but grip strength continues to improve for up to a year. Some patients notice the thumb is slightly shorter and a little weaker than before, but pain relief is reliable.
- Splint and injection trial: 3-6 months
- After trapeziectomy, sling and splint: 4-6 weeks
- Hand therapy after surgery: 3 months
- Full recovery of pinch and grip: 6-12 months
What results can I expect?
Excellent. Conservative treatment manages symptoms in many patients for years. When surgery is needed, around 90% of patients are highly satisfied with the result. Pain relief after trapeziectomy is reliable and long-lasting, even though full strength recovery takes time.
In numbers
Typical activity timelines for this condition. These are approximate and vary considerably between patients. Always follow the specific guidance given by your surgeon and hand therapist.
| Activity | Typical timeline | Notes |
|---|---|---|
| Drive | 4-6 weeks after trapeziectomy | When the cast or splint is off and you can grip the wheel and perform an emergency stop comfortably.[3] |
| Shower | Cast / splint covered | Use a waterproof cover. After full removal (around 4-6 weeks), washing as normal. |
| Light pinch tasks | 6-8 weeks after surgery | Gentle pinch and grip start under hand therapy guidance. Avoid heavy pinch loading early.[2] |
| Desk work | 2-3 weeks after trapeziectomy | Office-based work with the cast or splint in place, full keyboard use later once the splint is off.[1] |
| Manual work / gripping | 3-4 months | Heavy gripping returns gradually as pinch strength rebuilds.[1] |
| Full hand strength | 6-12 months | Pinch strength continues to improve through the first year. Some patients have permanent mild pinch weakness, but pain relief is reliable.[1] |
| Sport | 3-6 months | Racquet sports and gripping sports return as strength and comfort allow. |
Common concerns from patients with this condition or recovering from treatment, and whether they are expected or worth mentioning to your team.
- 1.British Society for Surgery of the Hand: Thumb base arthritis
- 2.British Association of Hand Therapists: Patient information leaflets
- 3.Royal College of Surgeons of England: Driving after surgery guidance
References are to UK clinical guidance and patient information from recognised organisations. This page is for general information and does not replace personalised advice from your own clinical team.
Going to have surgery?
If your team has recommended an operation for this condition, our step-by-step prep guide covers what to expect.
Hand therapy guide
Phased exercise programme, key precautions, and what to expect from rehabilitation for this condition.
How is it diagnosed?
- ✓Clinical examination, tenderness at the base of the thumb
- ✓Grind test, axial compression and rotation reproduces pain
- ✓Crank test, circumduction reproduces grinding
- ✓Plain X-rays, staged using the Eaton-Littler classification (Stage 1-4)
- ✓Assessment of MCP joint hyperextension and Z-deformity
Recovery milestones
- •Splint and injection trial: 3-6 months
- •After trapeziectomy, sling and splint: 4-6 weeks
- •Hand therapy after surgery: 3 months
- •Full recovery of pinch and grip: 6-12 months