The carpometacarpal joints of the fingers are synovium-lined ellipsoidal-type joints formed by the articular surface of the carpal bones proximally and the base of the second through fifth metacarpals distally (Fig. 76.1). The primary function of the carpometacarpal joints of the fingers is to aid in palmar cupping, which allows the hand to grasp objects (Fig. 76.2). The articular cartilage of the carpometacarpal joints of the fingers is susceptible to damage, which, if left untreated, will result in arthritis with its associated pain and functional disability. Osteoarthritis is the most common form of arthritis that is seen in the carpometacarpal joints of the fingers, which results in pain and functional disability, with rheumatoid arthritis, posttraumatic arthritis, and crystal arthropathy also causing arthritis of the carpometacarpal joints of the fingers. Less common causes of arthritis-induced pain of the carpometacarpal joints of the fingers include the collagen vascular diseases, infection, villonodular synovitis, and Lyme disease. Acute infectious arthritis of the carpometacarpal joints of the fingers joint is best treated with early diagnosis, with culture and sensitivity of the synovial fluid, and with prompt initiation of antibiotic therapy. The collagen vascular diseases generally manifest as a polyarthropathy rather than a monoarthropathy limited to the carpometacarpal joints of the fingers, although pain of the carpometacarpal joints of the fingers secondary to the collagen vascular diseases responds exceedingly well to ultrasound-guided intra-articular injection.

Patients with pain of the carpometacarpal joints of the fingers secondary to arthritis, gout, synovitis, and collagen vascular disease-related joint pain complain of pain that is localized to the base of the metacarpals. Activity, including pinching and grasping motions, makes the pain worse, with rest and heat providing some relief. The pain is constant and characterized as aching in nature. Sleep disturbance is common with awakening when patients roll over onto the affected wrist and hand. Some patients complain of a grating, catching, or popping sensation with range of motion of the joints, and crepitus may be appreciated on physical examination.

Functional disability often accompanies the pain of many pathologic conditions of the carpometacarpal joints of the fingers. Patients will often notice increasing difficulty in performing their activities of daily living and tasks that require grasping or pinching objects such as writing with a pen or pencil, opening a jar, or picking up a ball. If the pathologic process responsible for pain of carpometacarpal joints of the fingers is not adequately treated, the patient’s functional disability may worsen, and muscle wasting and ultimately a frozen carpometacarpal joints of the fingers joint may occur.

Plain radiographs are indicated in all patients who present with pain of the carpometacarpal joints of the fingers (Fig. 76.3). Based on the patient’s clinical presentation, additional testing may be indicated, including complete blood cell count, sedimentation rate, and antinuclear antibody testing. Magnetic resonance imaging or ultrasound of the carpometacarpal joints of the fingers joint is indicated if fracture, effusion, tendinopathy, crystal arthropathy, joint mice, synovitis, bursitis, or ligamentous injury is suspected (Fig. 76.4).

The carpometacarpal joints of the fingers are synovium-lined ellipsoidal-type joints formed by the articular surface of the carpal bones proximally and the base of the second through fifth metacarpals distally (see Fig. 76.1). The second metacarpal articulates primarily with the trapezoid and secondarily with the trapezium and capitate (Fig. 76.5). The third metacarpal articulates primarily with the capitate, with the fourth metacarpal articulating with the capitate and hamate. The fifth metacarpal articulates with the hamate. The carpometacarpal joints of the fingers are shaped differently than the first carpometacarpal joint in that the curvature of the distal articular surface of the base of the metacarpal is more dome shaped making for a more stable joint as it articulates with its corresponding carpal bones (Fig. 76.6). Each joint is lined with synovium, and the ample synovial space allows for intra-articular placement of needles for injection and aspiration. Compared to the first carpometacarpal joint, the carpometacarpal joints of the

fingers have a denser and tighter joint capsule and stronger transverse and interosseous ligaments. These differences combined with a much more limited range of motion when compared with the range of motion of the first carpometacarpal joint all contribute to greater joint stability, although fracture and subluxation still occur. The carpometacarpal joints of the fingers are also susceptible to overuse and misuse with resultant inflammation and arthritis.