What is Thumb Arthritis (CMC joint arthritis)?
Arthritis is a common condition that occurs when the cartilage that covers and protects a joint wears out. Without this cushioning, the bones in the joint grind against one another, wearing the joint down -causing pain and instability. Although there are several types of arthritis, Osteoarthritis and Rheumatoid Arthritis can both affect the thumb.
CMC joint arthritis occurs at the base of your thumb, where your thumb and wrist meet. Named for the bones that make up the base joint of the thumb – a Carpal (wrist) bone and a Metacarpal or long bone of the thumb – the (CMC) joint is the most common place in the hand for arthritis.
As the cartilage wears down, the ends of the bones rub together making it difficult to use your thumb. CMC joint arthritis can be mild or it can progress over time. As the disease progresses, the CMC joint may slip out of place causing the thumb to collapse into the palm, forming a “Z” or zigzag deformity. This makes it difficult to open the thumb away from the palm and makes grasping and pinching more difficult.
Symptoms of Thumb Arthritis:
- Pain at the base of the thumb, down by the wrist
- Pain when pinching or gripping, especially small objects like pens or tool handles
- “Grabbing” or sharp pain when you engage in a certain activity or even at rest
- The base of your thumb might “stick out” and look as though it is a little ledge or step
It is best to treat CMC joint arthritis early on with some simple measures. Generally treatment includes anti-inflammatory medicine to reduce pain and inflammation and a splint for support or rest. How much medication and what level of rest or support is needed depends on when the joint hurts, what makes it hurt, and how much it hurts.
It is important to look for a splint that supports the CMC joint without limiting motion more than is necessary. If you feel pain in your thumb only when you do certain tasks, choose a splint that supports but allows motion. If you feel pain even at rest, choose a splint that immobilizes the thumb. Often, because the pain from CMC joint arthritis tends to vary with activity, you may need both.
Short or hand-based splints that allow full or limited wrist motion and thumb motion can help. They are generally flexible splints that provide support by applying compression and may also include flexible stays or thin plastic inserts for added support.
For light support, the 3pp ThumSling (pictured below) supports the CMC joint and applies light compression to help reduce slipping and grinding on the joint.
Firm splints immobilize the thumb when full rest is needed. These splints can be recommended and custom fit by your healthcare professional.