Evaluation of the adult with thumb pain

INTRODUCTION — 

Thumb injuries are commonly encountered in primary care and emergency department settings. This topic will review how to perform the initial evaluation of patients with thumb pain, whether from injuries or other conditions. More detailed discussions of specific injuries and conditions affecting the hand are found separately:

●Common finger injuries: (See "Ulnar collateral ligament injury (gamekeeper's or skier's thumb)" and "Extensor tendon injury of the distal interphalangeal joint (mallet finger)" and "Evaluation and management of fingertip injuries".)

●Finger and hand fractures: (See "Distal phalanx fractures" and "Middle phalanx fractures" and "Proximal phalanx fractures" and "Digit dislocation reduction" and "Overview of metacarpal fractures".)

●Wrist injuries: (See "Evaluation of the adult with acute wrist pain" and "Distal radius fractures in adults" and "Scaphoid fractures" and "Overview of carpal fractures".)

●Medical conditions: (See "Gout: Clinical manifestations and diagnosis" and "Diagnosis and differential diagnosis of rheumatoid arthritis" and "Overview of hand infections" and "Clinical manifestations and diagnosis of osteoarthritis" and "Trigger finger (stenosing flexor tenosynovitis)".)

FUNCTIONAL ANATOMY — 

The thumb is composed of two phalanges, not three, as with other fingers. The distal and proximal phalanges articulate at the interphalangeal joint. The proximal phalanx articulates with the first metacarpal at the metacarpophalangeal (MCP) joint. The metacarpal is joined to the wrist at the carpometacarpal (CMC) joint, where it articulates with the trapezium. Finger and thumb anatomy are discussed in greater detail separately. (See "Finger and thumb anatomy", section on 'Thumb anatomy'.)

The thumb is spatially removed from the other digits, which makes it vulnerable to injury. This position and increased range of motion at the MCP and CMC joints allow the thumb greater movement than any other digit (picture 1). Nine muscles control the thumb's five primary movements (table 1).

One important and unique action of the thumb is opposition with other digits. The thumb functions as a mobile but stable "post," allowing the hand to grasp and pinch. Opposition requires the MCP and CMC joints to have some rotational capacity as well as flexion and extension.

Unless noted, movements are defined from a starting position with the thumb, the fingers, and the palm in the same plane. The thumb rests at a 45-degree angle from the axis of the palm and fingers.

HISTORY AND MECHANISM OF INJURY — 

For patients whose thumb pain is unrelated to trauma, the history should include the onset of pain and any associated symptoms, such as fever, numbness, and rash or other changes in skin color. Clinicians should inquire about activities or movements that provoke symptoms and any systemic symptoms or medical conditions.

For patients who have sustained recent trauma or have developed chronic post-traumatic thumb pain, clinicians should inquire about the mechanism and any prior medical or surgical treatment received. Common injury mechanisms include the following:

●Forced abduction and hyperextension at the metacarpophalangeal (MCP) joint, as might occur when a downhill skier falls while holding a planted ski pole, would be concerning for partial or complete tear of the ulnar collateral ligament.

●Crush injuries at the carpometacarpal joint may be associated with fracture or dislocation at the joint. A crush injury or axial load at the distal thumb may cause a tuft fracture of the distal phalanx.

●Fall onto an outstretched hand producing pain at the anatomic snuffbox suggests a scaphoid fracture.

●Fall onto a radially deviated closed fist may cause a trapezium fracture.

●Direct blow to the proximal phalanx that causes deformity should be treated as a phalangeal fracture until proven otherwise.

●Axial loading of a partially flexed metacarpal or forced abduction can cause a fracture at its base.

●Hyperextension can cause MCP and interphalangeal (IP) joint dislocations.

●Forced flexion of the IP joint can cause a mallet thumb.

EXAMINATION

●Inspection – Clinicians should inspect the thumb looking for erythema, edema, joint swelling, and skin lesions or color changes, then evaluate for deformity and laceration or other signs of injury, including nail bed injury, and assessment of the alignment of the thumb column and joints. Obvious deformity raises the question of fracture or dislocation. Deformity and soft tissue injury may coexist and management priorities are determined by the severity of each. Deep skin lacerations may expose fractured bone or torn tendon, which should be addressed first. Nail bed injuries and simple lacerations should be noted with treatment provided after completion of the examination.

●Palpation – Following inspection, proceed with palpation of the distal and proximal phalanges, first metacarpal, interphalangeal (IP) joint, metacarpophalangeal (MCP) joint, and carpometacarpal (CMC) joint for tenderness and deformity. Any sensory changes should be noted.

The differential diagnosis for pain at the joint without significant deformity includes subluxation, avulsion fracture of a muscle-tendon unit, and early-onset degenerative disease. Subluxation may be associated with joint instability. An avulsion fracture is usually associated with some weakness or joint instability. Early degenerative disease of the MCP or CMC joints can present with warmth, stiffness, joint pain, and swelling. Most patients describe a history of chronic or acute-on-chronic symptoms.

Palpation should include the sesamoid bones, found at the volar portion of the MCP joint. Inflammation of a sesamoid bone causes pain and discomfort, especially with pinching or grasping movements. Thumb trauma can fracture a sesamoid, causing similar symptoms. These fractures may be difficult to see on standard plain radiograph views. Additional radiographs with oblique views, ultrasound, or computed tomography (CT) scanning may be necessary. (See 'Diagnostic Imaging' below.)

●Motion and strength assessment – Next, ask the patient to perform all thumb movements without resistance, noting any abnormalities (picture 1 and table 2), then have the patient repeat these movements against active resistance, looking for weakness and instability by comparing the affected and unaffected sides (picture 2A-E).

The thumb tendons involved in extension can be palpated while the strength of the thumb is assessed. With the thumb extended, the tendons that form the "anatomic snuffbox" become prominent. The anatomic snuffbox is formed by the abductor pollicis longus and the extensor pollicis brevis tendons radially and the extensor pollicis longus tendon on the ulnar side (picture 3 and figure 1).

Thumb weakness or inability to perform a specific movement indicates damage to the muscle-tendon unit(s) responsible for that action, or less commonly, nerve injury or intra-articular conditions, such as infection or arthritis. In cases of injury, clinicians can combine their knowledge of functional anatomy with examination findings to identify the damaged muscle-tendon unit. (See "Finger and thumb anatomy", section on 'Thumb anatomy'.)

Minor joint instability (10 to 15 percent increase in motion compared with the unaffected side) may reflect a simple sprain of a ligament or capsule (picture 4). Larger discrepancies in joint motion between affected and unaffected sides or the complete inability to perform a movement suggest tendon or ligament rupture. The acutely injured patient may not permit an examination with this degree of precision due to pain. Examples of the examination of a ligament injury are provided in the accompanying images (picture 5 and picture 6 and picture 7). Treatment of tendon rupture varies by location. (See 'Joint instability' below.)

Substantial but incomplete tendon ruptures may not manifest weakness or significant instability and can be missed during the physical examination. Conversely, significant tendon or bone injuries may reduce joint mobility in specific planes if tendon or bone fragments become lodged in places that block motion (eg, interposed within joints).

The flexor tendons of the thumb should be assessed for nodules, and flexion and extension motion examined for signs of "sticking" or popping. Trigger thumb, or stenosing tenosynovitis, can occur if the flexor tendon develops a nodule or otherwise becomes larger than the pulley surrounding it. This can make movement of the flexor tendon through the pulley difficult and painful. Sometimes the digit becomes stuck in flexion. Subsequent extension occurs with discomfort and palpable popping. Nodules are most commonly found at the A-1 pulley of the flexor pollicis longus.

DIAGNOSTIC IMAGING

Plain radiographs — Plain radiographs, including anteroposterior (AP) or posteroanterior (image 1), lateral (image 2), and oblique views, are the initial studies obtained to assess thumb injuries. The lateral view should be a true lateral of the thumb, not a lateral of the hand. The AP of the thumb is best obtained with a Robert's view, wherein the forearm is placed in maximal pronation with the dorsum of the thumb lying directly on the radiograph cassette and the radiograph beam is shot at a 90-degree angle to the cassette (image 3). If a scaphoid fracture is suspected, a complete wrist series should be obtained, including a scaphoid view (image 4). (See "Scaphoid fractures", section on 'Diagnostic imaging'.)

When evaluating a metacarpophalangeal (MCP) joint that is not easily reducible or irreducible, a widened joint space on plain film raises concern for interposed soft tissue.

A plain radiograph of the carpometacarpal (CMC) joint can be difficult to interpret. A true lateral view of this joint (image 5) can be obtained by placing the forearm flat on the table with the hand in 20 degrees of pronation. The radiograph beam should be angled 10 degrees away from vertical (distal to proximal projection).

Stress views of the MCP (image 6) and CMC joints may be useful to evaluate joint stability. More than 30 degrees of MCP joint opening (or a relative increase of 15 degrees compared with the unaffected side) when an abduction stress is placed on the MCP joint raises suspicion for ligament rupture. Nonstress radiographs should be studied prior to obtaining any stress views to avoid converting a nondisplaced fracture into a displaced fracture.

Stress radiographs should be performed only by physicians with experience evaluating hand injuries. While some have expressed concern that stress imaging may cause a Stener lesion, biomechanical studies suggest this is unlikely (a Stener lesion occurs when the torn proximal end of the ligament becomes folded and trapped outside the adductor pollicis aponeurosis) [1]. Prior to obtaining stress radiographs, it is reasonable to discuss the approach to imaging with the hand surgeon who will assume care should relevant injuries be identified. Children should not have stress views if there is any concern for growth plate injury.

Computed tomography (CT) — CT is useful for evaluating complex fractures at the base of the thumb, when plain radiographs reveal the presence of such injuries. CT may provide additional information about stability of some fractures, such as Rolando and Bennett fractures. (See 'Fracture of the proximal phalanx' below and "First (thumb) metacarpal fractures", section on 'Intra-articular fractures'.)

Ultrasound — The introduction of small ultrasound transducers with frequencies as high as 22 MHz (picture 8) has substantially improved the imaging of thumb injuries, and ultrasound is commonly used in Europe and the United States for this purpose. For both the MCP and CMC joint, ultrasound can accurately define the degree of subluxation, degenerative change, and swelling [2]. In addition, direct visualization with ultrasound makes it easier to inject these smaller joints.

Dynamic ultrasound imaging can play an important role in evaluating the extent of partial tendon tears and can also confirm the diagnosis of conditions such as de Quervain tenosynovitis (image 7 and image 8). Fractures, bone spurring, and features of rheumatoid arthritis, gout, and pyrophosphate deposition disease, all have a characteristic appearance on ultrasound. Other pathologies such as trigger finger and ulnar collateral ligament injury (ie, gamekeeper's thumb or skier's thumb) may be diagnosed with dynamic ultrasound (image 9 and image 10).

There are many normal variants of the ligaments and the pulley system of the thumb. Diagnosis of small ligamentous tears must be made with caution and is best determined by a knowledgeable ultrasonographer or musculoskeletal radiologist. As an example, a full-thickness synovial recess is frequently seen at the base of the dorsal plate of the thumb MCP joint. This is a normal variant and should not be diagnosed as a tear [3].

Magnetic resonance imaging (MRI) — MRI may be useful for evaluating soft tissue injuries if the diagnosis remains unclear following clinical evaluation and imaging with plain radiographs and ultrasound. For some structures, three-dimensional sequences with the potential for reconstruction in non-orthogonal planes may be necessary [4].

DIAGNOSTIC APPROACH — 

Our approach to the assessment of adults presenting primarily for the evaluation of thumb pain is summarized in the following flow chart (algorithm 1). We begin by distinguishing thumb injuries sustained from trauma. Injuries associated with deformity consist of a fracture, dislocation, or some combination and are diagnosed with imaging, usually plain radiographs. Possible injuries are described below based on location. (See 'Deformity: dislocation and fracture' below.)

Injuries not associated with deformity are assessed by the history, including mechanism, physical examination, including testing for joint instability and focal tenderness, and possibly imaging depending on the initial findings. Possible injuries, including ulnar collateral ligament injury (skier's thumb), are described below based on location. (See 'Joint instability' below.)

If the examination of an injured thumb is unremarkable and joint function is grossly normal, minor soft tissue injury is likely present. Soft tissue injuries associated with a significant mechanism should be closely evaluated. (See 'Soft tissue injuries' below.)

Thumb pain not associated with recent trauma is most often due to flexor tenosynovitis, de Quervain tendinopathy, or a type of arthritis, including osteoarthritis, autoimmune (eg, rheumatoid), or inflammatory (eg, gout). These conditions are summarized below. (See 'Nontraumatic thumb pain' below.)

SOFT TISSUE INJURIES — 

Many thumb injuries involve lacerations. A simple laceration can be repaired once an examination is completed. Major skin and soft tissue wounds that extend to fractured bone, lacerated tendons, an open tendon sheath, or into a joint capsule must be managed immediately, including referral to a hand surgeon, as operative exploration is often necessary. Other indications for referral include large, grossly contaminated wounds. These may require tetanus prophylaxis. (See "Tetanus-diphtheria toxoid vaccination in adults", section on 'Immunization for patients with injuries'.)

Damage to skin or soft tissue that is deep but does not appear to extend to bone, joint, or tendon requires careful examination under sterile conditions to ensure there is no such involvement. Local anaesthesia is needed to perform the examination properly. (See "Digital nerve block" and "Upper extremity nerve blocks: Techniques".)

After copious irrigation with a sterile solution (eg, isotonic saline), a systematic inspection looking for any evidence of bone, tendon, or joint capsule injury should be performed. A laceration that is not grossly contaminated and reveals intact bone can be treated with irrigation and simple soft tissue and skin repair.

A subungual hematoma accompanies many thumb injuries (picture 9). These can be quite painful, but most are easily treated with trephination and drainage; removal of the nail is often not necessary. More extensive nail injuries can involve an open tuft (distal phalanx) fracture and nail avulsions. Partial or complete nail avulsions are usually associated with extensive nail bed injury, which must be repaired. The evaluation and management of subungual hematoma and related injuries are reviewed separately. (See "Subungual hematoma" and "Digital nerve block" and "Evaluation and management of fingertip injuries".)

DEFORMITY: DISLOCATION AND FRACTURE

General approach and management — Deformity of the thumb raises concern for fracture or dislocation. Fracture can occur in the distal or proximal phalanx, metacarpal, or trapezium, where the metacarpal articulates with the wrist. We recommend obtaining radiographs for any gross deformity. Imaging may not be necessary for bony tenderness not associated with joint instability or gross deformity, although it is reasonable to obtain in the setting of high-impact trauma. (See 'Diagnostic Imaging' above.)

The reduction of digit dislocations and adjunct procedures, such as digital blocks and sedation are discussed separately. (See "Digit dislocation reduction" and "Digital nerve block" and "Procedural sedation in children: Approach" and "Procedural sedation in adults in the emergency department: General considerations, preparation, monitoring, and mitigating complications" and "Upper extremity nerve blocks: Techniques".)

Deformity at the CMC joint — An isolated dislocation of the carpometacarpal (CMC) joint without an associated fracture is rare. The mechanism usually involves forceful flexion and dorsal translation at the thumb metacarpal base with or without an accompanying axial load [5]. More often, a crush injury (eg, thumb is stepped on or caught between two pieces of equipment), rather than a direct blow, is involved. Symptoms include pain and swelling at the base of the thumb, while metacarpal and multidirectional instability confirm the diagnosis. If a fracture or dislocation is suspected (ie, deformity, instability, or focal tenderness following trauma), plain radiographs should be obtained (image 11). (See 'Diagnostic Imaging' above.)

By the time patients present for medical evaluation, most dislocations of the CMC joint have completely or partially reduced, and diagnosis is made of a fracture or subluxation, or frequently both. Common fractures at the CMC joint involve the base of the metacarpal and can be stable or unstable (eg, Rolando fracture (image 12) and Bennett fracture (image 13)). (See "First (thumb) metacarpal fractures".)

Fractures of the scaphoid are common, and should be considered in the differential diagnosis of patients with pain proximal to the base of the thumb metacarpal, particularly if trauma to the thumb or hand was sustained (eg, fall onto an outstretched hand) (image 14) (see "Scaphoid fractures"). Fractures of the trapezium (carpal articulation of the thumb) are uncommon, with the mechanism typically involving a fall onto a radially deviated closed fist. (See "Trapezium and trapezoid fractures".)

Fractures involving any of the thumb joints can lead to arthritic changes. Therefore, CMC joint fracture or dislocation warrants referral to a hand specialist [6]. Depending upon the extent of injury, these fractures may be treated with closed reduction and percutaneous pinning or open reduction and internal fixation [5,7].

Deformity at the MCP joint — Metacarpophalangeal (MCP) joint (figure 2) dislocations are usually due to a hyperextension injury. Dislocations are classified as either "simple" or "complex" (figure 3 and image 15 and image 16).Simple dislocations, and sometimes subluxations (image 17), present with the proximal phalanx at an angle to the axis of the metacarpal; complex dislocations occur when there is overlap of the proximal phalanx and the metacarpal (the axes of the two bones are parallel). Simple dislocations can be managed by closed reduction with adequate anesthesia, while complex dislocations typically require operative intervention.

Most dislocations of the MCP joint are dorsal. In other words, the proximal phalanx becomes lodged on the dorsoradial surface of the metacarpal. Many dorsal dislocations present with the phalanx angled 60 to 90 degrees to the metacarpal with the articular surfaces remaining in contact. Closed reduction should be performed. (See "Digit dislocation reduction", section on 'Simple metacarpophalangeal or metatarsophalangeal dislocation'.)

Occasionally, the MCP joint dislocates in a volar direction. The force required for volar dislocations is greater and often causes significant damage to the joint capsule. Operative treatment is generally required, but an initial attempt at reduction is reasonable.

With complex dislocations, the volar plate becomes interposed in the joint space. The appearance can be similar to a simple dislocation, but often there is less angulation. Often, the proximal phalanx lies parallel to the metacarpal. The presence of soft tissue in the joint space complicates closed reduction, often making it impossible. Closed reductions may be attempted, but generally, they are best performed in the operating room by a hand surgeon [8].

Deformity at the IP joint — Interphalangeal (IP) joint dislocations are not common. The usual mechanism involves a hyperextension force exerted at the joint. Although frequently associated with a ligament or volar plate injury, IP dislocations are amenable to closed reduction most of the time. Sideline reductions without anesthesia can be performed. Irreducible IP joint dislocations likely involve interposed tissue and require referral for open reduction. (See "Digit dislocation reduction", section on 'Interphalangeal dislocation'.)

Fracture of the proximal phalanx — Proximal phalanx fractures usually result from a direct blow. The fracture can be transverse, oblique, or spiral. Angulation and rotation are common, and most fractures are unstable. If fracture is suspected, radiographs must be obtained and should include a true lateral and oblique view of the thumb (image 18). Some stable transverse fractures may be amenable to conservative management, but all spiral and oblique fractures are inherently unstable. Proximal phalanx fractures should generally be referred to a hand surgeon. (See "Proximal phalanx fractures".)

Fracture of distal phalanx (tuft fracture) — Distal phalanx fractures (ie, tuft fractures) usually result from a crush injury, but can also occur from an axial load. Fractures can be longitudinal, transverse, or comminuted ("crushed eggshell" appearance) (image 19), and significant soft tissue and nail bed injuries may accompany them. These fractures are usually stable. If angulation is minimal and the soft tissue is intact, treatment with a protective splint that extends to the proximal phalanx and prevents motion at the IP joint is generally adequate [9]. Three to four weeks of splinting is generally sufficient, but longer treatment may be helpful if pain or tenderness of the tuft persists. Most tuft fractures, even those with extensive comminution, heal in two to four weeks. (See "Distal phalanx fractures".)

Soft tissue injuries can be significant, sometimes involving nail avulsion and loss of fingertip pulp. We suggest obtaining hand surgery consultation for grossly contaminated injuries involving a fracture, irreducible or unstable fractures, transverse fractures of the distal phalanx with obvious angulation, or injuries associated with substantial soft tissue loss.

JOINT INSTABILITY — 

Minor joint instability (eg, 10 to 15 percent increase in motion compared with the unaffected side) may reflect a simple sprain. This can be treated with protective splinting, rest, and follow-up. Improvement should be noticeable within a few days. Support of the joint as the patient resumes activity may be useful (picture 10). If symptoms do not improve, we suggest further evaluation with diagnostic imaging. Greater joint instability suggests a more severe ligamentous injury, and immediate diagnostic imaging is indicated.

MCP joint instability — Collateral ligaments stabilize the metacarpophalangeal (MCP) joint against varus and valgus stress. However, trauma to the thumb MCP causing varus and valgus stress can injure the ulnar collateral ligament (UCL) or, less commonly, the radial collateral ligament (RCL) [10].

Ulnar collateral ligament injury (skier's thumb) — When the thumb is used to grasp a cylindrical object, such as a ski pole, baseball bat, or hammer, the UCL, which lies on the ulnar aspect of the thumb MCP joint (side closer to the index finger), is vulnerable to valgus stress (picture 7 and image 20). The mechanism for UCL sprain or rupture (sometimes called "skier's thumb") involves forceful abduction and hyperextension at the MCP joint, as might occur when a downhill skier falls, and their thumb is thrust against a planted ski pole.

The patient usually complains of pain at the ulnar aspect of the MCP joint and instability or weakness; examination reveals instability when valgus stress is applied to the MCP joint (picture 4). UCL injuries may involve Stener lesions, in which the torn proximal end of the ligament becomes folded and trapped outside the adductor pollicis aponeurosis, thereby distracting the torn ligament ends and preventing healing. Due to the importance of the UCL for thumb stability when grasping and the possibility of a Stener lesion, which can be difficult to diagnose clinically, referral to a hand surgeon is prudent when UCL injury is suspected. UCL injuries are discussed separately. (See "Ulnar collateral ligament injury (gamekeeper's or skier's thumb)".)

Radial collateral ligament injury — The RCL lies on the radial side of the thumb MCP (side farther from fingers). RCL injury occurs less often than UCL injuries but should be ruled out when thumb trauma occurs.

An RCL tear or sprain causes tenderness over the MCP joint on the radial side of the thumb and instability with varus stress. Clinicians can test for MCP instability by placing their fingers on the ulnar side of the patient's thumb and their thumb on the radial side of the patient's thumb at its tip, and then applying a varus force across the joint (picture 4). It is important to compare findings to the contralateral side as some patients have substantial joint flexibility at baseline. Pain without significant instability may reflect a simple sprain. Significant joint laxity, as demonstrated by a 15-degree difference in motion compared with the contralateral side, indicates a partial or complete ligament tear [11].

Unlike the ulnar side of the thumb, the radial side does not contain soft tissue structures that can lodge within the joint. If there is minimal instability and the joint functions normally, treatment with splinting for two to four weeks should be sufficient. Significant instability or joint dysfunction requires evaluation by a hand surgeon, as complete tears often require operative treatment.

IP joint instability — A relatively common cause of interphalangeal (IP) joint instability and inability to extend the thumb IP joint is rupture of the extensor pollicis longus (EPL) tendon, most commonly near Lister's tubercle, due to a nondisplaced or minimally displaced distal radius fracture. This can occur from mechanical or vascular insult to the tendon and can be delayed one to three weeks after the fracture occurs [12]. (See "Distal radius fractures in adults".)

Mallet thumb is a disruption of the terminal insertion of the extensor tendon onto the distal phalanx and can be a cause of IP joint instability. Mallet injuries occur much less often in the thumb than in the other fingers and differ from them in three ways:

●The EPL tendon is thicker at the distal end than the extensor tendons of the finger (extensor digitorum communis [EDC]).

●The thumb IP joint has a greater range of motion than fingers' distal interphalangeal joints.

●Greater forces are needed to rupture the EPL than the EDC, so the mechanism generally involves a hyperflexion injury in addition to significant axial load.

Early surgical repair of a mallet thumb may be desired because splinting the IP joint in extension with the thumb abducted (for protection) prevents athletes or heavy laborers from returning to activity. Conservative management consists of continuous splinting in extension for six weeks, followed by night splinting for an additional six to eight weeks. If nonoperative treatment fails, referral to a hand surgeon is reasonable, although the best surgical intervention for this uncommon injury remains unclear [13].

Thumb radiographs should be obtained in patients with IP joint instability if a bony avulsion of the distal extensor tendon is suspected. The presence of a large fragment warrants referral to a hand specialist, as operative repair may be needed.

NONTRAUMATIC THUMB PAIN

Stenosing flexor tenosynovitis (Trigger thumb) — Trigger thumb develops when the flexor tendon sheath thickens, creating a physical block to normal tendon movement via the pulley system. Symptoms include pain and tenderness at the base of the thumb on the palmar side or at the interphalangeal (IP) joint and worsen gradually. The patient may note a catching sensation when extending the thumb. After the thumb is flexed, it may "stick," requiring the patient to use their opposite hand to force the thumb back into extension. On examination, clinicians may note a palpable nodule along the tendon sheath on the palmar side. Trigger finger is discussed in greater detail separately. (See "Trigger finger (stenosing flexor tenosynovitis)".)

de Quervain tendinopathy — de Quervain tendinopathy is characterized by myxoid degeneration and thickening of the abductor pollicis longus and extensor pollicis brevis tendons and the sheath through which they pass in the first dorsal compartment of the wrist and may present as thumb pain. The condition generally presents as pain, sometimes with associated minor swelling along the radial aspect of the wrist extending to the base of the thumb. Pain is aggravated by activities requiring repetitive grasping with the hand in ulnar deviation. These activities include golf, racket sports, and fly fishing. The Finkelstein or Eichhoff tests may be used to help make the diagnosis. The Finkelstein test is performed by grasping the patient's thumb and deviating their thumb and wrist ulnarly, thereby stretching the involved tendons (picture 11). The Eichhoff test involves ulnar deviation of the wrist while the thumb is grasped by the patient's other fingers (picture 12). Treatment of de Quervain tendinopathy is discussed separately. (See "de Quervain tendinopathy".)

Arthritis — Joint pain at the metacarpophalangeal (MCP) or carpometacarpal (CMC) joints unrelated to trauma raises concern for arthritis [14]. This is particularly true if pain has been present for several months or longer. Osteoarthritis, inflammatory forms of arthritis (eg, psoriatic, gout), and autoimmune forms (eg, rheumatoid arthritis [RA]) can all affect the CMC joint.

Differentiating osteoarthritis from autoimmune causes such as RA can be difficult, particularly early in the course of disease, when symptoms from either condition may be similar and may affect both thumbs. Pain from osteoarthritis typically increases with joint use, while pain from RA typically is worse first thing in the morning and improves some with use. RA more often affects multiple joints and is commonly associated with systemic symptoms.

●Osteoarthritis – Osteoarthritis is a common cause of pain at the base of the thumb. Symptoms may be intermittent and typically involve the first CMC or scaphotrapeziotrapezoid joint, with pain focused in the deep thenar region or base. Pain is aggravated by sustained grasping or pinching (eg, sewing), or by forceful use of the thumb, such as turning a key. There may be a sensation of thumb weakness or of the joint "slipping." The metacarpal may be enlarged at its base, creating a mild deformity. There is typically no local warmth at the joint, but it is tender to palpation along the volar (or palmar) side. Applying an axial load to the metacarpal with slight rotation ("grind test") is painful. Crepitation may be noted. Strength testing frequently reveals loss of pincer strength. Characteristic changes are seen on plain radiographs (image 21). The evaluation and treatment of hand osteoarthritis are discussed in greater detail separately. (See "Clinical manifestations and diagnosis of osteoarthritis" and "Management of hand osteoarthritis".)

●Rheumatoid arthritis – RA primarily affects the thumb at the MCP and CMC joints. The first symptoms are usually joint pain and stiffness. Pain initially is from synovial inflammation that precedes cartilage or bone destruction. As synovitis progresses, the synovium thickens and small joint effusions occur, increasing thumb stiffness and impairing function. Ultimately, tendon laxity and joint deformity develop.

RA of the MCP joint can lead to a Boutonniere deformity (picture 13), while advanced disease at the CMC joint can lead to a Z deformity (also called "zig-zag" deformity) [15]. Subluxation of the extensor pollicis longus into a volar and ulnar position creates the Boutonniere deformity [16], defined as a flexed MCP joint combined with a hyperextended interphalangeal (IP) joint. The Z deformity involves MCP joint hyperextension combined with IP joint flexion and metacarpal adduction. RA in the hand is discussed in detail separately. (See "Articular manifestations of rheumatoid arthritis" and "Overview of the management of rheumatoid arthritis in adults".)

●Inflammatory arthritis (eg, gout) – Other inflammatory arthritides, such as gout, calcium pyrophosphate deposition (pseudogout), and psoriatic arthritis, may affect the thumb. Presenting symptoms include pain, swelling, and erythema. Gout and pseudogout can often be confirmed by synovial fluid analysis. Musculoskeletal ultrasound reveals synovitis and early bony changes. Plain radiographs may reveal chondrocalcinosis and bony erosions. (See "Gout: Clinical manifestations and diagnosis" and "Calcium pyrophosphate crystal deposition (CPPD) disease: Clinical manifestations and diagnosis" and "Clinical manifestations and diagnosis of psoriatic arthritis".)

Carpal tunnel syndrome — Pain and paresthesia along the median nerve distribution from carpal tunnel syndrome can be referred to the thumb along its palmar aspect (figure 4). Often, symptoms are first noticed at night and gradually worsen over weeks or longer. Assuming no other condition is present, palpation is unremarkable, and passive motion of the thumb is unaffected. Carpal tunnel syndrome is discussed separately. (See "Carpal tunnel syndrome: Clinical manifestations and diagnosis", section on 'Clinical features'.)

SUMMARY AND RECOMMENDATIONS

●Anatomy, mechanism, and examination – Thumb pain is a common complaint. The functional anatomy and examination of the thumb are described in the text. The history should focus on the mechanism of injury, while the examination should include assessment of all thumb movements (picture 1 and table 2) and joint stability. (See 'Functional anatomy' above and 'History and mechanism of injury' above and 'Examination' above.)

●Diagnostic imaging – Plain radiographs, including anteroposterior or posteroanterior, lateral, and oblique views, are the initial studies obtained to assess thumb injuries. Ultrasound can be useful for dynamic assessment of ligament and tendon injuries or imaging of other soft tissue pathology. CT or MRI may be needed to evaluate complex fractures. (See 'Diagnostic Imaging' above.)

●Diagnostic approach – Our approach to adults presenting primarily for the evaluation of thumb pain is summarized in the following flow chart (algorithm 1). Key distinctions are between non-traumatic and traumatic causes, and for the latter group among injuries associated with deformity, instability, or neither. (See 'Diagnostic approach' above.)

●Soft tissue injury – Thumb trauma often results in soft tissue injury. A simple laceration can be repaired once an examination is completed. Major skin and soft tissue wounds that extend to a fractured bone, lacerated tendons, or an open tendon sheath or joint capsule must be managed immediately, including referral to a hand surgeon. (See 'Soft tissue injuries' above.)

●Deformity following trauma – Obvious deformity of the thumb following trauma raises concern for fracture or dislocation. Fractures of the distal and proximal phalanges and dislocations of the metacarpophalangeal joint are most common. (See 'Deformity: dislocation and fracture' above.)

●Instability following trauma – Joint instability following thumb trauma suggests a ligamentous injury. Tears of the ulnar collateral ligament are most common. (See 'Joint instability' above.)

●Nontraumatic pain – Nontraumatic thumb pain usually represents a chronic or acute-on-chronic condition. Diagnoses to consider include stenosing flexor tenosynovitis (Trigger thumb), de Quervain tenosynovitis, arthritis, and carpal tunnel syndrome. Important elements of each diagnosis are described in the text, but more complete discussions are found separately. (See 'Nontraumatic thumb pain' above.)