Arthritis of
the Base of the Thumb
What is
arthritis of the base of the thumb?
Any condition
that irritates or destroys a joint is called
arthritis. In a normal joint, cartilage
covers the ends of the bones and allows them
to move smoothly and painlessly against one
another. With osteoarthritis (also called
degenerative arthritis), the cartilage layer
wears out and the bones rub against each
other. As the cartilage layer continues to
wear out, symptoms of arthritis develop and
the joint is eventually destroyed.
In the hand,
the second most common joint to develop
osteoarthritis is the joint at the base of
the thumb, or basilar joint. The basilar
joint of the thumb is formed by a small
wrist bone and the first bone of the three
bones in the thumb (see Diagram 1). The
shape of these bones gives the thumb a wide
range of movement – up and down, across the
palm, and the ability to pinch with each
finger.
Who gets
arthritis at the base of the thumb?
Arthritis in
the basilar joint of the thumb is more
common in women than in men. It usually
starts after age 40. Past injuries to this
joint such as fractures, sprains, etc., may
increase the chances of developing this type
of arthritis.
Signs and
symptoms of arthritis at the base of the
thumb.
The first
symptom of basilar joint arthritis is pain
with activities that involve gripping an
object with the thumb and fingers
(pinching). These activities could include
opening jars, turning door knobs, opening
car doors, and turning keys. Heavy use of
the thumb may also cause pain in the basilar
joint, as can changes in weather, such as a
change in humidity or temperature. As the
disease worsens, less activity is needed to
produce pain. Pinching strength decreases
and swelling may develop when using the
thumb. As the arthritis continues to worsen,
the basilar joint begins to look bigger and
“out-of-joint.” At this point, movement of
the thumb becomes limited.
How hand
surgeons diagnose arthritis at the base of
the thumb.
Close
inspection will sometimes show a lump at the
base of the thumb that can be swelling in
the joint or displacement of the thumb’s
first bone. Also, forcing the thumb firmly
against the wrist bone while moving the
joint will usually produce pain and may
produce a gritty feeling. The pain and
gritty feeling means that the bones are
rubbing against each other (see Diagram 2).
Early on, movement of the thumb is normal.
Later, movement becomes more difficult,
especially when sticking the thumb out to
the side. In worse cases, as the joint wears
away, the thumb’s first bone collapses into
the palm when gripping smaller objects. The
collapse of the first bone then causes the
second joint to overextend when gripping
larger objects (see Diagram 3).
Treatment for
arthritis at the base of the thumb.
The pain of
early basal joint arthritis will usually
respond to non-surgical treatment: limiting
movement of the thumb (placing a splint on
the thumb) and using medicine (oral or local
injection) to decrease swelling and pain.
Patients with more severe cases may require
surgery. Your doctor can advise you on the
best treatment for your situation.
Diagram 1
The basilar joint of the thumb is formed by
a small wrist bone (trapezium) and the first
of the three bones of the thumb
(metacarpal).
Diagram
2
The pain produced when moving the first
thumb bone back against the wrist bone in a
circular motion means that the bones are
rubbing directly against each other.
Diagram
3
In severe
cases, the thumb’s first bone collapses into
the palm causing the second bone to
overextend when grasping larger objects.
Copyright ©
American Society for Surgery of the Hand
2001
www.assh.org
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