Thumb Carpalmetacarpal (CMC) Arthritis

The joint at the base of the thumb, or the carpalmetacarpal (CMC) joint enables the thumb to swivel, pivot, and pinch so that you can grip things in your hand. When osteoarthritis occurs at this joint, the cartilage begins to wear down creating painful bone on bone friction.

Causes and risk factors

  • Females are more susceptible than men
  • Over 40 years of age
  • Doing activities with repetitive forceful pinching
  • Prior fractures


  • Pain when gripping or pinching
  • Swelling, tenderness, and limited motion at base of thumb
  • Lack of strength in grip and pinching activities
  • Bony prominence or bump on joint

Diagnosis and treatment

Most people that have thumb arthritis will notice that their symptoms gradually worsen over time. For patients that have thumb arthritis, it is usually good to avoid or delay surgery. There is no harm in waiting for surgery unless the pain is so bad that the patient cannot use the hand for a long period, and as a result may develop atrophy and weakness of the thumb muscles, known as thenar muscles.

Conservative treatment options include the following:

  • Bracing with a hand based splint. Neoprene based splints are more comfortable, but rigid thermoplastic splints provide better support.
  • Cortisone injections. These can provide relief for 6-12 months but may become less effective over time as the arthritis gets progressively worse.

When conservative care fails, surgery is a good option that should have results that will last a lifetime. The procedure is called a carpalmetacarpal (or CMC) arthroplasty. In this procedure, the entire bone in the wrist at the base of the thumb (trapezium) and all bone spurs are removed. If the patient has arthritis at the next thumb joint, or STT joint, then half of that bone is also removed and an additional arthroplasty surgery is performed. A tendon from the forearm is used to reconstruct the worn out ligament and create a spacer for the bone at the base of the thumb to rest on. After six weeks, patients can gradually start resuming activities.


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