Evaluation of the patient with thumb pain

INTRODUCTION — Injuries to the hand, wrist, and fingers, including the thumb, are common. According to the National Hospital Ambulatory Medical Care Survey for the year 2004, 11.3 percent of all visits to United States emergency departments involved such injuries [1].

This topic will review how to perform the initial evaluation of patients with thumb pain, whether from injuries or other conditions. Finger and thumb anatomy and detailed discussions of specific injuries and conditions are found separately. (See "Finger and thumb anatomy".)

For finger and hand injuries: (see "Distal phalanx fractures" and "Middle phalanx fractures" and "Proximal phalanx fractures" and "Digit dislocation reduction" and "History and examination of the adult with hand pain" and "Overview of metacarpal fractures").

For 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").

For other conditions: (see "Clinical manifestations and diagnosis of gout" and "Diagnosis and differential diagnosis of rheumatoid arthritis" and "Overview of hand infections" and "Clinical manifestations and diagnosis of osteoarthritis").

FUNCTIONAL ANATOMY — The thumb is composed of two phalanges, not three as with other fingers. The distal and proximal phalanges articulate at the interphalangeal (IP) 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.

MECHANISM OF INJURY — A thorough history should be obtained from the patient in cases of post-traumatic thumb pain. A mechanism of forced abduction and hyperextension at the metacarpophalangeal (MCP) joint, as might occur when a downhill skier falls and their thumb is thrust against a planted ski pole, would be concerning for partial or complete tear of the ulnar collateral ligament (UCL). Crush injuries at the carpometacarpal (CMC) joint may be associated with fracture or dislocation at the joint, whereas a crush injury or axial load at the distal thumb may result in a tuft fracture of the distal phalanx. A fall onto an outstretched hand with subsequent pain at the anatomic snuffbox suggests a scaphoid fracture, while a fall onto a radially deviated closed fist may cause a trapezium fracture. A direct blow to the proximal phalanx that causes deformity should be treated as a phalangeal fracture until proven otherwise. MCP and interphalangeal (IP) joint dislocations are usually due to a hyperextension injury, whereas forced flexion of the IP joint can cause a mallet thumb.

EXAMINATION — Examination of the thumb begins with inspection for deformity and laceration or other signs of injury, including nail bed injury. Assess 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 are noted and treatment is provided after completion of the examination.

Following inspection, palpate the distal and proximal phalanges, first metacarpal, interphalangeal (IP) joint, metacarpophalangeal (MCP) joint, and carpometacarpal (CMC) joint for tenderness and deformity. The differential diagnosis for pain at the joint without significant deformity includes subluxation and 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 and erythema, in addition to joint pain and swelling, and most patients will describe a history of chronic or acute-on-chronic symptoms.

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 snuff box is formed by the abductor pollicis longus (APL) and the extensor pollicis brevis (EPB) tendons radially and the extensor pollicis longus (EPL) 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 intraarticular 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 to the unaffected side) may reflect a simple sprain. Larger discrepancies in joint motion between affected and unaffected sides or the complete inability to perform a movement suggests tendon rupture. Examples are provided in the accompanying images (picture 4 and picture 5 and picture 6). The treatment of tendon rupture varies with the location. (See 'Joint instability' below.)

Clinicians should note that 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).

DIAGNOSTIC IMAGING

Plain radiographs — Plain radiographs, including anteroposterior (AP) or posteroanterior (PA) (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 an 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 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. Non-stress radiographs should be studied prior to obtaining any stress views to avoid converting a nondisplaced fracture into a displaced fracture. 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 15 MHz 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 imaging in particular plays an important role in evaluating the extent of partial tendon tears and can also confirm the diagnosis of entities, such as de Quervain tenosynovitis. Fractures, bone spurring, and features of rheumatoid arthritis all have a characteristic appearance on ultrasound, while entities, such as trigger finger and ulnar collateral ligament injury (ie, gamekeeper’s thumb), may also be diagnosed.

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].

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), perform a careful, systematic inspection looking for any evidence of bone, tendon or joint capsule injury. A laceration that is not grossly contaminated and reveals intact bone can be treated with irrigation and simple soft tissue and skin repair.  

Possible joint capsule injury can be confirmed by injection with colored fluid. One approach is to mix sterile isotonic saline with a few drops of fluorescein and inject the liquid into the joint capsule away from the laceration site. Approximately one or two mL of fluid should be sufficient. Fluorescein stained fluid will not leak from the joint if the capsule is intact.

Many thumb injuries are accompanied by a subungual hematoma. 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 is 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 be unnecessary for bony tenderness without 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 CMC joint without an associated fracture is rare. The mechanism usually involves forced adduction of a flexed thumb or a direct axial load [5]. Most often a crush injury (eg, thumb is stepped on or caught between two pieces of equipment), rather than a direct blow, is involved. Symptoms are pain and swelling at the base of the thumb. Multidirectional instability confirms the diagnosis. If a fracture or dislocation is suspected (ie, deformity, instability or focal tenderness following trauma is present), obtain plain radiographs (image 7). (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 (eg, Rolando fracture (image 8)) or unstable (eg, Bennett fracture (image 9)). (See "First (thumb) metacarpal fractures".)

Fractures of the scaphoid are common, and should be considered in the differential diagnosis of patients with pain just proximal to the base of the thumb, particularly if trauma to the thumb or hand was sustained (eg, fall onto an outstretched hand) (image 10). (See "Scaphoid fractures".) Fractures of the trapezium (carpal articulation of the thumb) are uncommon. The mechanism typically involves 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 [7].

Deformity at the MCP joint — MCP joint dislocations are usually due to a hyperextension injury. Dislocations are classified as either “simple” or “complex” (figure 2 and image 11 and image 12). Simple dislocations, and sometimes subluxations (image 13), 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 require operative intervention.

Most dislocations of the MCP joint are dorsal. In other words, the proximal phalanx becomes lodged on dorsoradial surface of the metacarpal. Many dorsal dislocations present with the phalanx angled 60 to 90 degrees to the metacarpal. The articular surfaces remain 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 — 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 is 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 14). 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 15), 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 injury 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 to 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 7). If symptoms do not improve, we suggest further evaluation with diagnostic imaging. Greater joint instability suggests a more severe ligamentous injury.

MCP joint instability — Collateral ligaments stabilize the MCP joint against varus and valgus stress. However, such stress can injure the ulnar collateral ligament (UCL) or, less commonly, the radial collateral ligament (RCL).

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 side of the thumb next to the index finger, is vulnerable to valgus stress (picture 6 and image 16). The mechanism for UCL sprain or rupture (often 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. UCL injuries may involve Stener lesions, in which the torn proximal end of the ligament becomes folded and trapped outside the aponeurosis, thereby 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 radial collateral ligament (RCL) lies on the radial side of the thumb, farthest from the fingers. RCL injury occurs less often than injuries of the ulnar collateral ligament, 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. 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 to the contralateral side, indicates a partial or complete ligament tear [10].

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

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

●The thumb IP joint has a greater range of motion than fingers’ distal interphalangeal joints (DIP).

●Greater forces are needed to rupture the EPL than the EDC so the mechanism of injury generally involves more than just an axial load.

Early surgical repair of a mallet thumb is often needed 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, refer the patient for operative management [11].

We suggest obtaining radiographs in patients with IP joint instability to look for bony avulsion of the distal extensor tendon. 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 IP joint. 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’s tenosynovitis — de Quervain’s tenosynovitis is an inflammation of the abductor pollicis longus (APL) and extensor pollicis brevis (EPB) tendons. It presents as pain and sometimes swelling at the radial styloid, extending toward 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’s test (ulnar deviation of the wrist with the thumb grasped in the palm by the fingers) is often used to help make the diagnosis (picture 8). Symptoms of short (weeks) duration may improve with immobilization. (See "de Quervain tendinopathy".)

Arthritis — Joint pain at the MP or CMC joints unrelated to trauma raises concern for arthritis [12]. This is particularly true if pain has been present for several months or longer. Both osteoarthritis and rheumatoid arthritis can affect the CMC joint.

Osteoarthritis is a common cause of pain at the base of the thumb (CMC joint). Symptoms often include diffuse pain that 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 enlarge 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 side. Applying an axial load on the metacarpal with slight rotation (the “grind test”) is painful. Crepitation may also be noted. Strength testing frequently reveals loss of pincer strength. Typically, characteristic changes are evident on plain radiographs. The evaluation and treatment of osteoarthritis is discussed separately. (See "Clinical manifestations and diagnosis of osteoarthritis" and "Overview of the management of osteoarthritis".)

Rheumatoid arthritis (RA) primarily affects the thumb at the MP 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 MP joint can lead to a Boutonniere deformity, while advanced disease at the CMC joint can lead to a swan neck deformity. Subluxation of the EPL into a volar and ulnar position creates the Boutonniere deformity, defined as a flexed MP joint combined with a hyperextended IP joint. The swan neck deformity involves MP joint hyperextension combined with IP joint flexion and metacarpal adduction.

Rheumatoid arthritis is discussed in detail separately. (See "Clinical manifestations of rheumatoid arthritis" and "General principles and overview of management of rheumatoid arthritis in adults".)

Carpal tunnel syndrome — Pain and paresthesias along the median nerve distribution from carpal tunnel syndrome can be referred to the thumb along its palmar aspect (figure 3). 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 '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 injuries or imaging of other soft tissue pathology. Computed tomography may be needed to evaluate complex fractures. (See 'Diagnostic Imaging' 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 either phalanx 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 and mallet thumb 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’s 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.)