Rudolph's Pediatrics, 22nd Ed.

CHAPTER 199. History and Physical Examination in Rheumatology

Robert P. Sundel

Extremity complaints are common in children; they are estimated to account for up to 10% of nonwell child visits to pediatricians’ offices.¹ Conversely, rheumatologic conditions, are rare, affecting fewer than 200,000 children in the United States. Thus, clinicians caring for children need an efficient and effective means of distinguishing arthritis, lupus, and other autoimmune conditions from injuries, infections, tumors, and noninflammatory causes of extremity complaints. This chapter will discuss the key components of a focused history and physical examination useful for rapidly narrowing down the possible explanations of a child’s musculoskeletal ailment. The next chapter discusses laboratory and imaging studies that may be used to confirm the caregiver’s clinical suspicions.

EPIDEMIOLOGY

The reported incidence and prevalence of musculoskeletal diseases in children worldwide vary significantly. For example, among more than 30 epidemiological studies of juvenile arthritis, new cases are reported to arise at a rate of 0.008 to 0.226 per 1,000 children, yielding a reported prevalence of 0.07 to 4.01 per 1,000 children.^2,3 Although there are likely geographic, genetic, and environmental factors that result in true variations in the likelihood of developing rheumatologic conditions, several additional factors also contribute to reported differences. First among these is the fact that most pediatric rheumatologic conditions are diagnosed on the basis of clinical criteria rather than definitive laboratory or imaging findings. New signs may develop over time, leading to reclassification of conditions. Thus, children treated for ankylosing spondylitis may later develop colitis, thereupon qualifying for a diagnosis of Crohn disease. Arthritis that resolves after one year may be called monocyclic juvenile arthritis by some caregivers, transient or postinfectious arthritis by others. Despite these uncertainties, outcomes in virtually all autoimmune conditions are optimized by expeditious diagnosis and early initiation of effective therapy. Recognition of signs and symptoms suggestive of rheumatologic conditions is thus essential for everyone who provides healthcare to children.

PATHOPHYSIOLOGY

The presenting symptoms of musculoskeletal conditions are more dependent upon the location of the abnormality than upon the specific diagnosis. Thus, fractures, tumors, and osteomyelitis all present with pain that may awaken the patient from sleep because of the constant stimulation of sensory nerves by lesions within bone. Conversely, for unknown reasons, children with arthritis seldom complain of pain; more than 90% of children with joint or extremity pain do not have arthritis, and more than 90% of those with arthritis do not complain of pain.⁴ Inflammatory arthritis may cause children to limp or lose milestones because joint effusions cause distension of the joint capsule and discomfort with motion. Pain, however, is generally absent. Thus, differences in the location, timing, and characteristics of a child’s symptoms enable a pediatrician to rapidly narrow the potential causes of musculoskeletal complaints. Confirmation of the suspected diagnosis may then be obtained from physical exam findings, often without need for further investigations.

When a child presents with a musculoskeletal complaint, it is helpful to categorize the symptoms according to the nature of onset (acute versus chronic), the number of sites involved, and whether there is evidence of systemic or extra-articular involvement. It is also important to remember that most normally active children will have a history of trauma during the preceding 24 hours. Unless the trauma is significant, however (typically a football injury, automobile accident, or bicycle fall), it is more likely to have unmasked preexisting pathology than to have caused pathology in the resilient tissues of a child’s musculoskeletal system. Thus, 10% to 20% of osteogenic sarcomas present after trauma, but in none of these cases does the accident represent anything more than a signpost for the problem.⁵

GENETICS

Although there is a strong genetic component to most rheumatologic and inflammatory disorders, generally polygenic rather than monogenic factors are at work as reviewed in Chapter 198.⁶ Many of the genes appear to confer a general susceptibility to developing autoimmune diseases rather than a predilection for a particular syndrome.⁷ Thus, a family history of psoriasis, inflammatory bowel disease, thyroid disease, or multiple sclerosis is potentially significant and may be associated with an increased likelihood that a child has arthritis. In most cases, however, having a parent with a particular autoimmune condition, such as rheumatoid arthritis, does not further identify children as being at risk for developing the same disease.

CLINICAL FEATURES

HISTORY

Key elements of the history that help identify the cause of symptoms include the complaints’ timing, character, and nature. Thus, knowing whether pain is dull, sharp, radiating, or burning may suggest whether the source is bone, soft tissue, or nerve. Alleviating and exacerbating factors, particularly response to activity, help distinguish rheumatologic from orthopedic conditions. Questions may have to be posed in a variety of ways in order to extract useful information, and interrogation of several different people may reveal subtle nuances of critical importance. Further, in younger or nonverbal children who are not able to articulate the specifics of their symptoms, observations of the parents and other caregivers may have to substitute for the patient’s description. Nonetheless, the time spent obtaining a thorough and precise history is invariably repaid many times in the information it yields (see Table 199-1).

INFLAMMATORY CONDITIONS

The single most characteristic feature of discomfort related to inflammatory processes is the classic morning stiffness of arthritis. Difficulties are also often reported after naps or other periods of inactivity such as long car rides, movie watching, or sitting in classes at school (the so-called theater sign). This is thought to be the result of decreased hyaluronic acid in inflamed synovial fluid, leading to gelling and reduced lubrication at physiologic temperatures. Thus, children with arthritis typically feel better after a warm bath or several minutes of activity. These help to raise the temperature within the joint, in turn allowing the synovial fluid to return to the liquid state in which it lubricates most efficiently. Accordingly, a child with arthritis may suffer joint stiffness in the morning, but may be quite comfortable exercising strenuously later in the day. It is decidedly atypical for inflammatory arthritis to awaken children from sleep. Cold, damp weather, or swimming in cool water tends to be more difficult for children with arthritis, whereas warm weather generally relieves symptoms. An atypical symptom profile—especially nighttime pain or pain with activity—should raise suspicion of an alternative diagnosis, even in the setting of what appears clinically to be an arthritic joint.

Table 199-1. Categories of Musculoskeletal Pain

MECHANICAL PAIN

The timing of mechanical pain is essentially the mirror image of the pattern of inflammatory pain. Children typically feel well in the morning, whereas the more active they are, the more discomfort they have; chondromalacia patella is called runner’s knee for a reason. Like inflammation, however, mechanical pain does not generally awaken children from sleep. Rest and ice tend to alleviate mechanical symptoms, as opposed to the activity and heat that are typically salubrious in arthritis. Once the broad category causing a child’s symptoms is determined, the precise type of overuse syndrome or injury can generally be determined from a careful history and physical examination. Demographic information is also helpful: An adolescent boy experiencing knee pain while playing basketball is more likely to have Osgood-Schlatter syndrome, whereas aching knees in a 12-year-old girl on the cross-country team are more likely to result from iliotibial band syndrome. Even if the precise cause of discomfort is not apparent, at the very least, the caregiver may be confident that consultation with an orthopedist is likely to be more useful than referral to a rheumatologist when pain has the characteristics of a mechanical problem.

BONY PAIN

Pain originating in the osseous compartment tends to be constant, and does not change significantly with activity. Bone pain raises concerns for infection, trauma, and malignancy. Although inflammatory and mechanical pains do not usually awaken children at night, bony pain may do so, particularly when related to leukemia or other tumors. Consequently, when a history of nighttime awakening is elicited, special consideration must be given to possible oncologic etiologies. Cytopenias are typically seen with leukemia, although a normal complete blood count (CBC) does not absolutely exclude the possibility. Other tumors, such as sarcomas or metastatic neuroblastoma, are far less common, but they, too, must be considered in children with pain consistent with a bony origin.

NEUROPATHIC PAIN

Nerve pain tends to be worst at bedtime, when the usual focus on daily activities is no longer available to distract the child. In children old enough to describe the sensation, neuropathic pain typically has a burning or lancinating character. It is also commonly associated with allodynia, severe hypersensitivity of overlying normal soft tissues. Although joints may be involved, neuropathic pain generally encompasses extra-articular areas as well, and it may follow a dermatomal distribution. Activity does not have a significant effect on neuropathic pain. The complaints associated with chronic pain syndromes are also most characteristic of neuropathic pain. Thus, if pain is sharp or radiating, but is not associated with identifiable trauma, tumors, neuropathy, or vasculitis, then pain syndromes such as fibromyalgia or reflex sympathetic dystrophy should be considered. Although pain syndromes are traditionally regarded as diagnoses of exclusion, this is both an inefficient and an undesirable way to arrive at such a conclusion. First, having numerous tests and studies tends to confirm families’ suspicions that symptoms are owing to a rare condition that is evading the clinician’s grasp. Second, prolonged searches for organic etiologies tend to amplify and reinforce symptoms. Thus, when pain that does not fit any apparent temporal or anatomic pattern is accompanied by significant dysfunction, including school absences, pain syndromes should rise to the top of the list of diagnostic possibilities. Further support, such as other family members with a dysfunctional response to pain (eg, prolonged disability after apparently minimal trauma, or severe cases of fibromyalgia or irritable bowel syndrome), should allow accelerated diagnosis and treatment of pain syndromes (see Chapters 113 and 207).

PHYSICAL EXAMINATION

Assessment of a child with musculoskeletal complaints must include both a general examination and a complete assessment of the musculoskeletal system. This is facilitated by the results of the history: If a child has evidence of an inflammatory condition involving multiple joints, then signs of systemic conditions such as inflammatory bowel disease and systemic lupus erythematosus should be sought. Conversely, monoarticular pain would point toward mechanical, infectious, or proliferative conditions.

It is often useful to begin by having the child run in the examining room or down the hall. This is unexpected and enjoyable for most children, and therefore might alleviate anxiety. Further, most children find it difficult to focus on running while consciously altering their movements, so true pathology is likely to be revealed. Conversely, children are often self-conscious when asked to walk, potentially altering their movements and misleading the examiner. Absolute refusal to run, especially in an older child, might also yield important clues of a volitional or functional component to the complaints.

When observing a child who is running, it is important to remember that a normal gait is the most efficient and stable means for a bipedal creature such as a human to ambulate. In order to cause one’s gait to be altered, strong countervailing forces must be present. These may be anatomic (eg, broken bone, unstable skeleton) or sensory (loss of proprioception or balance) in nature, with pain the most common cause of a disrupted gait in children.

Different types of pathology result in predictable alterations in a child’s movement. Lower-extremity involvement is most common in rheumatologic conditions, and assessment of gait is therefore a particularly useful tool. Although formal gait analysis is not necessary, recognizing specific abnormalities will facilitate localization and identification of specific conditions. For example, abnormalities in the pelvis, hip, or upper femur cause a child to favor the involved area, often resulting in leaning to the involved side and substituting support using the bones of the pelvis and upper leg for the usual flexion of the hip or contraction of the pelvic muscles. The result is hip circumduction and/or a Trendelenburg gait. By corollary, such a gait can be caused only by pathology involving the proximal femur or the pelvis. Knee involvement, conversely, causes loss of full flexion and extension of the knee, and results in a gait with a characteristic 30-degree knee flexion (the most comfortable, neutral position for that joint). Similar considerations for additional sites of pathology are listed in Table 199-2.

Once the child’s gait has been observed, a complete and systematic examination should be performed. Observation is the most sensitive tool for detecting abnormalities, as these are likely to be evident as subtle asymmetries between the right and left sides (Fig. 199-1). Assessment of range of motion should then focus particularly on the areas of asymmetry. As long as the examiner is familiar with joints’ normal appearance and range, evaluation of either passive or active range of motion will yield the necessary information. Pathology typically first becomes evident at the extremes of range of motion: cervical arthritis, for example, leads to loss of extension at the neck, whereas sternocleidoid muscle weakness leads a child to avoid neck flexion. In both cases, the final degrees of motion are lost first, so assessment of joints only at the midranges of movement is not adequate.

Table 199-2. Site-Specific Alterations in Gait in Rheumatologic Conditions

The next component of the exam is palpation. Examiners are understandably reluctant to cause undue discomfort in a child, but overly gentle palpation is useless: If a child does not complain of pain at any stage of the exam, it is impossible to know whether this represents an absence of pathology or simply a failure to reach the threshold for pain. Thus, at least one area must be palpated forcefully enough to evoke an “Ouch!” from the child. The amount of pressure used may then be compared to palpation at other sites in order to provide a means of differentiating healthy from affected areas. The knee may exhibit a ballottable effusion, meaning that applying pressure directly to the patella forces it downward, displacing synovial fluid and causing it to bounce against the femur. The characteristic springiness is not noted when fluid does not intervene between patella and femur, as in healthy children. The joint may also be swollen from synovial proliferation, which has a boggier consistency than the free fluid of a joint effusion.

FIGURE 199-1. Asymmetry of ankles, with subtle fullness adjacent to right medial malleolus identifying abnormal joint.

Signs of inflammation are the hallmark of arthritis. Warmth and swelling are most characteristic, whereas overlying erythema is more characteristic of septic arthritis. The child with a chronic inflammatory arthritis may report that she is uncomfortable, but this is more commonly described as stiffness than as pain. In fact, at least 20% of children with juvenile arthritis never complain of pain; in a study from Oklahoma, only 13 of 226 children referred to a rheumatology clinic with joint pain actually had arthritis.⁴

Careful examination of an inflamed joint also may allow estimation of the duration of the arthritis. Synovitis is characterized by increased blood flow, typically more pronounced in the portion of the joint compartment subjected to the maximum force. In the knee this is the medial aspect, where hyperemia leads to increased delivery of nutrients and accelerated growth. Initially, this may be seen as prominence of the medial femoral condyle, later as genu valgus. Ultimately, the leg with the inflamed knee grows more rapidly and a leg length discrepancy develops.⁸ The lower leg may bow in order to compensate for the greater length. At the same time, the knee loses extension and develops a flexion contracture, with resultant atrophy of the vastus medialis muscle. In contrast, significant inflammation in the hip often damages the growth plate and leads to foreshortening of the involved leg. Since minimal longitudinal growth occurs at the distal tibia, ankle arthritis causes little if any discrepancy in leg lengths.

DIFFERENTIAL DIAGNOSIS

PATTERN OF JOINT INVOLVEMENT

In addition to categorizing the type of pain a child is experiencing, it is critical to determine how many joints are affected. The potential causes of a monoarticular process differ significantly from those of polyarticular conditions, so careful examination of all joints is mandatory even when the complaint involves only a single location. It is also important to determine the type of onset (sudden or gradual), duration of symptoms, and any associated systemic features such as fever or rash. Distinct differential diagnoses must be considered for monoarticular and polyarticular processes, as well as for joint complaints associated with fever or other extra-articular signs and symptoms (see Table 199-3).

Monoarthritis

The potential etiologies of a monoarticular process may be narrowed down by consideration of the nature of onset and duration of symptoms.

Acute onset When a monoarticular process involving pain and swelling of a single joint starts acutely, bacterial infections must be excluded. Unlike most types of inflammatory arthritis, where delaying the diagnosis by several days is unlikely to have long-term implications, treatment of septic arthritis must not be postponed. In fact, a history of fever associated with a single red, swollen, painful, or hot joint necessitates arthrocentesis for cell count and culture. Conversely, in an afebrile child, traumatic injury is a more likely explanation for acute joint symptoms. It is helpful if there has been clearly documented antecedent trauma, but this may be difficult to elicit in young children who are unable to verbalize specifics of the history. In patients with an underlying bleeding disorder such as hemophilia, routine daily activities may cause hemarthrosis.

Table 199-3. Common Causes of Arthritis

Once these possibilities are excluded, postinfectious or “reactive arthritis” must be considered in the case of an acutely symptomatic joint. This process may involve one or many joints, but it characteristically causes less inflammation than an acute infection. Thus, postinfectious arthritis does not usually cause erythema overlying the joint, and although it may be uncomfortable, excruciating pain is uncommon. Reactive arthritis generally responds well to nonsteroidal anti-inflammatory agents, and is typically transient. Lyme disease may also be difficult to distinguish clinically from septic arthritis, though generally it causes more indolent symptoms.⁹

Subacute onset Diagnostic considerations of an isolated, chronically swollen joint differ from those related to an acute arthritis. Bacterial infections are far less likely, whereas lower grade infections, especially Lyme disease in endemic areas, must be excluded. Chronic monoarthritis also may be caused by Mycobacterium tuberculosis, particularly in immunocompromised children. Also within this category are chronic forms of synovitis, especially pauciarticular juvenile arthritis and psoriatic arthritis. Rarer inflammatory arthropathies, such as arthritis due to sarcoidosis, may also cause monoarthritis. Primary tumors of the cartilage and synovium, although extremely rare, are also most likely to present as discomfort in a single joint. The most common of these, pigmented villonodular synovitis (PVNS), typically causes a chronically painful and swollen knee. A nontraumatic arthrocentesis that yields bloody fluid is suggestive of an articular tumor.

Polyarthritis

When several joints are involved, rheumatologic conditions rise to the top of the differential diagnosis. Most common among these is polyarticular juvenile arthritis, although other autoimmune diseases such as systemic lupus erythematosus and vasculitis typically involve multiple joints as well. Infections are instead progressively less likely as more joints are involved, with the exceptions of gonococcal arthritis in sexually active or abused children, and salmonella arthritis in immunocompromised patients. Arthritis associated with systemic conditions, such as inflammatory bowel disease or cystic fibrosis, must also be considered. Usually, extra-articular involvement (such as a new murmur in rheumatic fever or hives in serum sickness) offers a clue to these conditions. The pattern of joint involvement may also be suggestive: rheumatic fever, vasculitis, and serum sickness characteristically cause a migratory polyarthritis, whereas most other conditions cause additive or fixed involvement of multiple joints. In general, children with polyarthritis are most likely to benefit from consultation with a pediatric rheumatologist.

PROGNOSIS AND OUTCOMES

Rheumatologic conditions typically take long periods of time to be diagnosed. The average delay in diagnosis of arthritis varies from a few weeks in children with systemic onset juvenile arthritis (likely owing to its acute, dramatic presentation with hectic fever, rash, and arthritis) to more than 6 months in dermatomyositis (with the more indolent and subtle loss of physical ability). Current treatment protocols stress the importance of early, aggressive therapy, because chronic joint damage may start becoming evident within six months of the onset of synovitis.¹⁰ Thus, the most important thing that caregivers can do for children with suspected rheumatologic disorders is to expeditiously and efficiently diagnose their condition.¹¹ Overlooking key points in the history and physical exam or referring to the wrong specialist are among the most common causes of delays in diagnosis; focusing on mechanical or infectious causes of joint complaints and obtaining imaging studies or performing arthrocenteses in a child with morning stiffness will only delay the initiation of treatment for arthritis. By remembering that most rheumatologic conditions in children are clinical diagnoses established on the basis of history and physical exam, and simply confirmed by laboratory studies and imaging, caregivers can avoid delays and optimize outcomes.