The causes of joint pain may be classified as infectious, postinfectious, rheumatologic, autoinflammatory, hematologic, oncologic, mechanical/traumatic, and other (including genetic and metabolic) (Table 11–1).
Infectious and Postinfectious
Septic arthritis is an infection of the joint space, usually caused by hematogenous spread rather than direct inoculation or spread from contiguous tissues. Septic arthritis is typically bacterial (e.g., Staphylococcus aureus, Streptococcus pyogenes, Neisseria spp.), although the spirochete Borrelia burgdorferi (Lyme disease) may be found in the synovium during acute infection. The presentation is typically acute. Prompt diagnosis and treatment with an appropriate antibiotic is necessary to preserve articular cartilage, which may begin to degrade as early as 8 hours after the onset of a suppurative infection.1 Of special importance is septic arthritis of the hip, which does not typically present with noticeable joint swelling or redness, making it more difficult to distinguish from less emergent causes of hip pain. In viral arthritides, such as in parvovirus B19, viral particles may be found in the synovium, but the arthritis may be immune complex-mediated.
The peak incidence of septic arthritis is in children younger than 3 years, with boys affected more frequently than girls. Knees and hips are most commonly involved, followed by ankles, elbows, and shoulders, but any joint may be affected. S. aureus is by far the most common organism responsible for septic arthritis, with other common organisms varying by age and other risk factors (e.g., N. gonorrhea for sexually active adolescents).1,2 Septic arthritis typically presents with a single exquisitely tender, swollen, erythematous, warm joint with decreased range of motion and pain. The child is often, but not always, febrile and toxic appearing. Although the large majority of cases of septic arthritis affect only one joint, multifocal arthritis is noted in 5–15% of cases.1–5 The presence of a known rheumatologic condition, such as juvenile idiopathic arthritis (JIA) or systemic lupus erythematosus (SLE), does not preclude the possibility of developing septic arthritis, especially when being treated with immunosuppressive medications.6–8 Septic arthritis is discussed in more detail in Chapter 48.
Postinfectious “reactive” arthritis occurs following either bacterial or viral infections. Reactive arthritis presents with an acute onset of severe joint pain and swelling, sometimes with associated erythema, and can occur days to weeks following genitourinary or enteric infections. Poststreptococcal reactive arthritis and acute rheumatic fever occur following untreated group A β-hemolytic streptococcal pharyngitis, most commonly in children 5–15 years old. In acute rheumatic fever, arthralgias may precede a migratory arthritis that usually affects large joints, such as knees, ankles, shoulders, wrists, or elbows. The Jones Criteria for the diagnosis of acute rheumatic fever are presented in Table 11–2.9 Postinfectious viral processes occur 1–2 months following infection, yet most are transient and resolve within 6 weeks. Toxic synovitis is a mild reactive arthritis of the hip. It commonly occurs following a viral upper respiratory tract infection.
Table 11–2. Jones Criteria for Diagnosis of Acute Rheumatic Fever* (JAMA 1992) ||Download (.pdf)
Table 11–2. Jones Criteria for Diagnosis of Acute Rheumatic Fever* (JAMA 1992)
Joint: migratory polyarthritis
Carditis: new murmur, (mitral ≥ aortic)
Previous acute rheumatic fever or rheumatic heart disease
Nodules, subcutaneous, and painless
Elevated inflammatory markers (ESR or CRP)
Prolonged PR interval on ECG
Rheumatologic and Autoinflammatory
Previously referred to as juvenile rheumatoid arthritis (JRA), JIA affects approximately 0.1% of children.10 By definition, JIA begins before the 16th birthday and symptoms must be present for a minimum of 6 weeks. JIA is divided into seven subsets: systemic arthritis, oligoarthritis, polyarthritis (rheumatoid factor negative), polyarthritis (rheumatoid factor positive), psoriatic arthritis, enthesitis related arthritis, and undifferentiated arthritis.11 A key distinction is between systemic arthritis and other forms of JIA. Systemic arthritis is defined as arthritis in one or more joints associated with high fevers for at least 2 weeks and “quotidian” for at least 3 days, accompanied by one or more of the following characteristics: (1) evanescent, nonfixed, erythema-tous rash, (2) generalized lymph node enlargement, (3) hepatomegaly and/or splenomegaly, or (4) serositis. Children are often ill-appearing, particularly during fever spikes, when the rash may be more prominent. Arthritis may be present at initial diagnosis or may become evident later in the disease course, consisting of oligoarthritis or polyarthritis with involvement of any joint.
Other forms of JIA typically present with mild or no constitutional symptoms and variable degrees of pain. Approximately 25% of children with these forms of JIA will have no pain associated with their arthritis. The oligoarthritis subtype most commonly affects the knees or ankles. It typically occurs in young girls and is associated with antinuclear antibody (ANA) positivity and asymptomatic anterior uveitis. Polyarthritis often involves both large and small joints, sometimes in a symmetric pattern. It may be more debilitating, especially if rheumatoid factor is present. Enthesitis-related arthritis may be a harbinger of juvenile ankylosing spondylitis, which is more common in males, involves the sacroiliac joints and spine, and is strongly associated with the presence of HLA-B27. In psoriatic arthritis, the joint symptoms may precede the onset of rash. There is often a family history of psoriasis, prominent nail pits, and painful dactylitis, which has the appearance of a “sausage digit.” Arthritis in association with growth delay, weight loss, microcytic anemia, and hypoalbuminemia should alert the clinician to the possibility of inflammatory bowel disease, even in the absence of specific gastrointestinal complaints.
SLE is a multisystem disorder often presenting with fever, fatigue, arthritis, and rashes, including the typical malar “butterfly” rash. Approximately 15% of all cases of SLE present during childhood, most commonly after 8 years of age, with a greater prevalence in females.12 At presentation, arthritis and rash are present in 70% of children, and nephritis is observed in 50%.
Juvenile dermatomyositis is an autoimmune disorder that presents with rash and progressive proximal muscle weakness. The common “heliotrope” rash is a violet discoloration of the upper eyelids, which are often puffy. A malar rash may be seen. Gottron papules are erythematous lesions seen on the dorsum of the hand, particularly over the metacarpophalangeal as well as proximal and distal interphalangeal joints. Erythematous discoloration of the extensor surfaces of the elbows and knees are common. Up to 60% of children develop nondeforming oligoarthritis or polyarthritis during the course of their disease, but fewer (6–35%) have evidence of arthritis on initial presentation.13,14
The two most common vasculitides of childhood are both associated with joint symptoms.15 Henoch–Schönlein purpura is a small vessel vasculitis that presents with palpable purpura in dependent areas (usually lower extremities), acute arthritis of the lower extremities (usually knees and/or ankles), and abdominal pain, with or without renal involvement. Kawasaki disease is diagnosed by the constellation of fever (5 days or more) and four of the following: nonsuppurative conjunctivitis, changes of the lips and oral cavity (red cracked lips, strawberry tongue), polymorphous rash, cervical lymphadenitis (nonsuppurative lymph node enlargement greater than 1.5 cm), and swelling of the hands and feet. The incidence of arthritis in Kawasaki disease is as high as 45%.16 Two forms of arthritis have been described, and resolve without sequelae. Arthritis or arthralgia found in the acute stage is characterized by polyarticular involvement of large and small joints. Arthritis in the subacute phase of Kawasaki disease tends to involve the hips, knees, and ankles. Timely treatment decreases risk for long-term coronary artery aneurysms.16 Arthritis is a common feature of other less common vasculitides, such as polyarteritis nodosa and the antineutrophil cytoplasmic antibody (ANCA) associated vasculitides (Wegener granulomatosis, microscopic polyangiitis, Churg–Strauss syndrome).
Sarcoidosis is a chronic systemic granulomatous disease that can affect almost any organ system. A common presentation during childhood consists of arthritis, rash, and uveitis, particularly in the inherited form associated with mutations in CARD15.17 The majority of patients will have constitutional symptoms, such as malaise, fevers, and weight loss. Hilar, mesenteric, and peripheral lymphadenopathy are common findings.
Arthritis may be a prominent feature of autoinflammatory syndromes. Acute attacks of arthritis are seen in conditions such as familial Mediterranean fever, tumor necrosis factor receptor-associated periodic syndrome, hyper-IgD syndrome, Muckle–Wells syndrome, and familial cold autoinflammatory syndrome (see Chapter XXX for more detail).18 In neonatal-onset multisystem inflammatory disease, arthritis may be transient, but a typical severe, deforming arthropathy is usually observed.
Neoplasms that may present with joint complaints include primary liquid tumors (leukemia), metastatic disease, benign synovial tumors, and osteoid osteoma. Distinguishing malignancies from rheumatologic illnesses in a child presenting with arthritis and systemic symptoms is challenging. For example, in 15–30% of acute lymphoblastic leukemia cases, fever and joint pathology may be seen.19 Leukemia and neuroblastoma are the most common malignancies that present with joint symptoms. However, other malignancies (such as lymphoma and Ewing's sarcoma) have also been initially misdiagnosed as rheumatologic illnesses delaying appropriate treatment.20,21 Some features that are atypical for rheumatologic diseases and warrant further workup include: bone pain or tenderness, back pain, night sweats, focal neurologic abnormalities, and bruising.21 Marrow replacement often causes pain that is worse at night, involves the back and long bones, and may be out of proportion to physical examination findings.20
Trauma is a common cause of musculoskeletal complaints in children and adolescents. Prior to maturation of the skeletal system, fractures are more common than ligament or tendon injury. Thus, it is important to image sites of trauma to ensure proper stabilization (surgical vs. nonsurgical) and suggest orthopedic referral. Nonaccidental trauma should always be considered, especially in the case of a neonate, an infant, or a chronically ill child, and in the case of an injury not explained by the proposed mechanism. In a child with multiple fractures or deformities, genetic or metabolic predisposition to such injuries should also be considered. A history of trauma does not preclude the presence of infectious, neoplastic, or rheumatologic condition. In fact, parents often mistakenly attribute the chronic joint swelling of JIA to a minor episode of trauma.
Consider Legg–Calvé–Perthes, or idiopathic osteonecrosis of the proximal femoral epiphysis, especially in a boy 4–8 years old, who presents with painless limp. Pain may develop in the hip, knee, or thigh.22 This pain is usually worse at the end of the day and may wake a child from sleep. Slipped capital femoral epiphysis is seen in older children and adolescents. Slipped capital femoral epiphysis causes acute or subacute knee, thigh, or hip pain and is especially prevalent in overweight or obese individuals. Bilateral disease is observed in 20–30% of cases and urgent orthopedic referral is indicated.22,23