Osteoarthritis of the thumb is more common in women than men. Usually, osteoarthritis of the thumb develops after 40 years of age.
Cause of Thumb Osteoarthritis
Osteoarthritis is a degenerative joint disease. Osteoarthritis causes cartilage -- a tough but flexible tissue that covers the ends of the bones forming a joint -- to wear away gradually. Thumb osteoarthritis most commonly affects the joint at the base of the thumb, also known as the basal joint or the carpometacarpal joint (CMC joint). The CMC joint is formed where the metacarpal bone of the thumb attaches to the trapezium bone of the wrist.
Bad sprains or fracture of the thumb can damage articular cartilage (cartilage that covers ends of bones in a joint). Injury to the CMC joint of the thumb, even if cartilage damage is not immediate, can affect the movement of the thumb joint. If the joint becomes misaligned following injury, wear and tear on that joint increases, eventually leading to osteoarthritis.
Diagnosis of Thumb Osteoarthritis
Diagnosis of thumb osteoarthritis is, in part, based on the patient's medical history. Past hand injuries, especially to the thumb itself, may indicate why osteoarthritis developed in the thumb joint.
A physical examination can reveal abnormal range of motion in the CMC joint, swelling, and pain or tenderness at the base of the thumb. Crepitus (a grinding sound as the joint is moved) suggests the ends of the bones that form the joint are rubbing against each other.
Symptoms of Thumb Osteoarthritis
Pain is the primary symptom associated with thumb osteoarthritis. Initially, pain is present with movement or activity (e.g., turning a key, opening a door, lifting a cup). As osteoarthritis progresses, pain is present even during inactivity or rest. Other symptoms of thumb arthritis include:
- difficulty gripping objects
- swelling, stiffness, or tenderness at the base of the thumb
- enlarged appearance of the CMC joint
- limited range of motion
Osteoarthritis can also cause the CMC joint of the thumb to loosen and bend back too far, referred to as hyperextension. A particular deformity, known as thumb swan neck deformity, can also occur when the middle thumb joint is flexed and the CMC joint is hyperextended.
Treatment of Thumb Osteoarthritis
Early osteoarthritis of the thumb can be effectively treated using nonsurgical treatment options, for example:
- nonsteroidal anti-inflammatory drugs (NSAIDs) to reduce inflammation and swelling
- icing the joint for 5 to 15 minutes several times a day to relieve inflammation and swelling
- physical therapy or occupational therapy
- splinting to restrict movement of the thumb
- steroid injections into the joint
Surgical options include:
- CMC joint fusion (arthrodesis) -- an option for patients looking for pain relief who are not overly concerned about losing fine thumb motion
- joint replacement or arthroplasty -- plastic or metal prostheses are used to replace the CMC joint (prosthesis serves as a spacer after the arthritic surfaces of the bones in the CMC joint are removed)
- excision arthroplasty -- removes arthritic surfaces of CMC joints and replaces it with some material (e.g. rolled up piece of tendon) to keep bones separated
- Trapeziectomy -- removal of a small bone called the trapezium
Arthritis of the Thumb. American Academy of Orthopaedic Surgeons. July 2007.
Arthritis of the Thumb. Orthogate. July 28, 2006.