The CMC joint is the point where the wrist and thumb meet and is comprised of the metacarpal bone and the trapezium, which is one of the eight carpal bones.

The CMC joint allows for a wide range of movements. It allows us to flex the thumb across the Palm, extend the thumb away from the
palm, abduct, and oppose.

This extensive mobility allows us to grasp and manipulate objects of various sizes and shapes to carry out our daily activities.

What happens in a normal joint?

A joint is comprised of two bones and each edge of the bone is covered with cartilage.  The joint is housed within a joint capsule, which is then bathe in synovial fluid. This allows the joint to glide smoothly along each other for optimal mobility.

When you have arthritis, the cartilage begins to wear away and the bones begin to rub against each other creating friction. Subsequently, an increase synovial fluid is released, resulting in inflammation.

Due to increase friction, the involved bones become enlarged and bone spurs develop. In turn, decreased joint stability occurs.

Who is at risk?

1. Females older than 40 years of age
2. Persons whose jobs require prolonged joint force on the thumb. (For instance, a baker, a carpenter or a seamstress)
3. Trauma to the thumb can increased risk of CMC joint arthritis.
A thumb sprain or a fracture, may lead to decreased stability.

What are the symptoms?

  • The main symptom is pain along the base of the thumb.
  • Swelling
  • stiffness in the joint
  • Weakness (difficulty opening bottles, turning key, cutting foods due to decreased pinch strength)

How do we treat this?

Early intervention is always the key to success.
See a hand therapist, as soon as you start to notice any of the symptoms listed above.

  1. The first step to take is to get a brace. Usually, a thumb spica brace is  recommended for support. The brace should be worn when performing an activity that elicits pain. You may need a more rigid splint depending on how severe symptoms are.

Rigid Orthosis

Neoprene Brace (soft)

2. Incorporate joint protection techniques during your daily activities to prevent increase stress on thumb CMC joint.


The following are examples of joint protection techniques:

– Instead of using a small joint of the thumb joint and putting force on the thumb, use your entire palm and press when using a bottle with pump dispenser.

– Rather than lifting a heavy container with one hand, share the weight between both hands.

– Slide heavy objects across a surface to help protect your joints.

– Assistive devices are also recommended to facilitate independence with daily activities (i.e. jaw twister). The jar twister is very soft and comfortable and easy on your joints. This device will allow you to open a jar without putting as much force on the CMC joint.


Twister Jar Opener

A home exercise program is a vital part of treatment.  

1. move your thumb away from the palm and then flex you thumb across the palm.  If this painful for you, you can always use the uninvolved hand to assist with the movement. 

2. Move your thumb across the palm, towards the pinky finger. 

3. Slide the thumb from the tip to the base of the pinky finger or to your pain free range

4. Oppose each finger with the thumb. 

(Perform each of these exercises about 10-15 times 1x/day.) 

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