Osteoarthritis is when the cartilage is loosening and its quality gets gradually worse and finally it disappears partly or completely. The defective cartilage causes an uneven load that makes the joint unstable. The basal joint of the thumb is particularly exposed to osteoarthritis especially among women over 40.

Possible causes
Heredity.
An earlier injured joint may age/ grow old faster with osteoarthritis as result.

Symptoms
Local pain in and around the joint.
Motion pain may increase over the years, intense pain may appear.
Resting pain.
The basal joint may be swollen, warm and sore from contact and pressure.
The opening grip decreases.

Treatment
A firm splint or an elastic thumb brace.
A night splint to counteract malposition.
Ergonomic advice.
Technical devices.
Injection of cortisone may relieve the pain effectively.