The thumb has 3 joints
Basal Joint Arthritis is also known as degenerative joint disease (DJD) or carpometacarpal (CMC) arthritis.
Thumbs contribute 40-60% of the use of our hands and allow us to complete both delicate and forceful tasks.
Potential Causes of Basal Joint Arthritis:
- Cumulative trauma from repetitive tasks
- Repeated forceful pinching
A 5 pound pinch at the thumb tip can create over 25 pounds of force at the CMC joint!
Thumb motion and function is accomplished by a complex balance of the different muscles that control the thumb and index finger. In a normal thumb, these muscles work together to move the thumb correctly and with precision. When there is basal joint arthritis, the muscles become unbalanced causing abnormal movement patterns.
An imbalance in the muscles causes uneven pressure at the cmc joint. This causes changes to the cartilage that covers the bones (osteoarthritis). More muscle imbalance occurs as the joint shifts position, the result is pain, loss of motion and loss of function.