Carpal-metacarpal Osteoarthritis
What causes CMC OA?
The exact cause is unknown. Genetics, old
injuries such as a fracture or dislocation,
and/or generalized joint laxity may
predispose some people to develop of this
type of “wear and tear” arthritis.
CMC OA at the base of the thumb occurs
more often in women than men, particularly
women over the age of 40, but both women
and men can have CMC OA.
What is carpal-metacarpal
osteoarthritis (CMC OA)?
In normal joints, cartilage covers the ends
of bones and acts like a shock absorber
allowing smooth, pain-free movement. In
osteoarthritis (OA, or “degenerative arthritis”)
the cartilage layer wears out, resulting
in bone-on-bone contact, pain, and joint
deformity.
One of the most common hand joints to
develop OA is the base of the thumb, called
the carpal-metacarpal (CMC) or basal joint.
This highly specialized saddle-shaped joint is
formed by a small wrist bone (trapezium) and
the long bone (first metacarpal) of the thumb.
The CMC joint of the thumb is a very mobile
joint that allows for a wide range of motion
including up, down, and across the palm
(opposition), and strength during pinch.
How is CMC OA diagnosed?
Your provider will take a detailed health
history including existing medical conditions,
how the hands are used, whether there are
any prior injuries, and perform a physical
evaluation. X-rays are used to confirm the
diagnosis and determine the extent of joint
changes. Symptom severity does not always
correlate with x-ray findings.
Signs and Symptoms
• Dull, achy, or sharp pain at the base of
the thumb
• Pain with activities requiring pinching
– such as opening jars, turning door
knobs or keys, and writing
• Pain may also occur at rest or at night
• A bump, called a “shoulder sign,” may
develop at the base of the thumb
• The MP joint may bend backwards
(hyperextend) as it has to compensate
for limited motion or pain at the CMC
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Carpal-metacarpal Osteoarthritis
What is the treatment for
CMC OA?
Currently, there is no cure for arthritis. But
there are many treatment options to help
relieve your symptoms.
Mild-moderate CMC OA symptoms often
respond well to non-surgical care. The goal
of treatment is symptom management in
order to relieve pain and improve function.
Treatment may include:
• Splinting the thumb – intermittent use
of a splint is a good long-term strategy to
help minimize pain and/or decrease stress
to the CMC joint during daily activities.
• Activity modification – changing or
avoiding symptom provoking activity
may help reduce pain. Using different
equipment – such as an ergonomic
keyboard, tools with a pistol grip, or a key
holder – helps reduce stress to the joint.
• Heat and cold – can be used 3-4x/day for
10-15 minute sessions. Heat is typically
helpful in reducing stiffness and achy
pain, while cold packs may help reduce
inflammation and pain. Use whichever
makes your hands feel better.
• Topical pain relievers – over-thecounter creams/ointments/gels may help
temporarily decrease pain.
• Hand Therapy – one or two sessions with
a hand therapist can provide education
and strategies for activity modification,
joint protection techniques, splint(s), and a
specific home program of range of motion
and strengthening exercises.
• Anti-inflammatories – non-steroidal antiinflammatory (NSAID) medications such as
acetaminophen (Tylenol™), ibuprofen
(Advil™), or naproxen (Aleve™) may help
manage pain and should be used as
directed by your provider.
• Cortisone injection – an injection of
this anti-inflammatory into the CMC joint
may help decrease pain. Response to the
injection will vary from person to person
and relief is usually temporary.
If or when non-surgical treatment is
no longer providing adequate relief of
symptoms, surgery may be an option.
A consultation with your hand surgeon can
help decide the best course of treatment for
you.
Additional resource for information on CMC OA
• American Society for Surgery of the Hand – assh.org
• American Academy of Orthopaedic Surgeons – aaos.org or orthoinfo.org
The content provided here is not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the
advice of your physician or another qualified health provider with any questions you may have regarding a medical condition.
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