Basal joint arthritis, also known as first carpometacarpal (CMC) joint arthritis, is a common form of degenerative joint disease affecting the thumb. The joint at the base of the thumb wears down over time, leading to pain and a loss of hand function. As a prevalent type of hand osteoarthritis, it significantly impacts daily activities that require pinching or gripping, particularly in the aging population.
Defining the Basal Joint and Arthritis
The basal joint is the thumb’s carpometacarpal (CMC) joint, located where the metacarpal bone of the thumb connects to the trapezium bone in the wrist. This unique saddle-shaped joint allows for the thumb’s wide range of motion, including opposition, which makes grasping and pinching possible. Because its design prioritizes mobility, the joint is inherently less stable than others, relying heavily on surrounding ligaments for support.
Basal joint arthritis is a form of osteoarthritis that develops when the smooth articular cartilage covering the ends of these bones begins to wear away. As the protective cartilage deteriorates, the bones start to rub against each other, generating friction and causing inflammation. This process leads to pain and swelling, and can ultimately result in joint instability and a loss of proper alignment due to the weakening of supporting ligaments.
Recognizing the Signs
The most common sign of basal joint arthritis is a deep, aching pain located at the base of the thumb. This discomfort is often aggravated by motions that require forceful pinching or gripping, such as opening a jar, turning a key, or writing. In the early stages, pain may only occur with activity, but as the condition advances, patients may experience pain at rest and even at night.
Patients frequently report a noticeable decrease in their ability to pinch or grip objects firmly, along with stiffness, particularly in the morning. The joint may appear swollen and tender to the touch, especially over the trapezium bone. In more advanced stages, the misalignment of the metacarpal bone can create a visible “bumpy” or squared-off appearance at the base of the thumb. Diagnosis is typically confirmed through a physical examination, including the grind test to reproduce symptoms, along with X-rays that show characteristic joint space narrowing.
Identifying Risk Factors
Age is a primary factor in developing basal joint arthritis, with the condition becoming progressively more common in individuals over 40 years old. Gender plays a notable role, as the condition is significantly more prevalent in women than in men, particularly postmenopausal women.
Genetic predisposition and a family history of arthritis can also contribute. Previous trauma or injury to the thumb joint, such as fractures or ligament tears, can destabilize the joint and accelerate the degenerative process years later. Additionally, occupations or hobbies that involve repetitive, forceful motions of the thumb, such as assembly line work or certain musical instruments, may place increased stress on the joint.
Treatment Approaches
The management of basal joint arthritis typically begins with non-surgical, conservative treatments aimed at reducing pain and maintaining function. Activity modification is often recommended, which involves avoiding or altering actions that provoke pain, such as using specialized tools or changing how objects are gripped. Splinting or bracing the thumb is a common intervention, using flexible neoprene supports during the day and more rigid splints at night or during rest to reduce inflammation.
Over-the-counter anti-inflammatory medications, known as NSAIDs, can help manage pain and swelling. If oral medications are insufficient, a physician may recommend a corticosteroid injection directly into the basal joint. This injection can provide substantial pain relief for several months, though the effect is temporary and may diminish over time. Occupational therapy is also beneficial, offering instruction in joint protection techniques, ergonomic adjustments, and specific exercises to preserve range of motion and strength.
When conservative treatments fail to provide adequate relief, or when the arthritis is severely advanced, surgical intervention may be considered. The most common surgical procedure is a trapeziectomy, which involves removing the entire trapezium bone to eliminate the bone-on-bone grinding. This procedure is frequently combined with ligament reconstruction and tendon interposition, where a piece of tendon is used to stabilize the thumb and create a cushion in the space left by the removed bone.
Arthrodesis, or joint fusion, locks the joint in a fixed position to provide a stable, pain-free thumb for forceful activities, though it eliminates all motion at the joint. Joint reconstruction procedures, including the use of joint implants, are also sometimes performed to preserve motion. Recovery from surgery involves a period of immobilization, typically four to eight weeks in a cast or splint, followed by extensive hand therapy to restore movement and strength.