Introduction

Musculoskeletal (MSK) symptoms are a common presentation of children to primary care and emergency departments. Painful joints and/or limping are presenting features of a wide range of conditions, many of which do not primarily affect the MSK system. Appropriate management requires targeted history taking and directed yet comprehensive examination to narrow the differential diagnosis before selection of investigations. A practical approach considers the differentials filtered by the age of the child, pattern of joint involvement and chronicity of symptoms. We will also highlight ‘red flags’ pointing to serious conditions that may rarely be seen in primary care.

The overall prevalence of MSK pain during childhood has been estimated to be 25–50% . In many cases, this is benign and self-resolving; therefore, it is not brought to medical attention. However, epidemiological surveys have highlighted that MSK complaints are a common presentation to primary care representing around 7% of all paediatric attendances , and they are the third leading reason for primary care presentation among adolescents in the USA . In one study, MSK symptoms also represented 3% of paediatric day-case non-elective admissions . A retrospective study in a paediatric primary care clinic in Spain identified the prevalence of MSK pain increasing with age from 2.4 to 5.7% at age 3 years to 27.5–36% at age 14 . The most common presentations were knee arthralgias, other joint arthralgias (ankles, wrists and small joints of the fingers) and soft tissue (muscles, ligaments and tendons) pain comprising 65% of complaints across all age groups. Hip pain was reported significantly more frequently in the preschool-age group, whereas heel and back pain was more common among adolescents.

In this review, we will provide a guide to differential diagnosis through comprehensive and targeted history taking and examination leading the reader to appropriate investigation and referral to secondary care.

The clinical approach

When faced with a child with joint pains in primary care, initial consideration of the range of differential diagnoses will drive the appropriate history and examination. Although comparatively uncommon, several diseases presenting with MSK symptoms can lead to mortality and long-term morbidity; therefore, they should be actively considered and excluded. These include primary and secondary malignancies, septic arthritis, osteomyelitis, inflammatory arthritis and non-accidental injury/child abuse. Only one in 10,000 children have MSK pain as the primary presenting feature of cancer , although around 20% of children with leukaemia and 2% of those with lymphoma have some MSK symptoms at diagnosis . By far, the most common cause for MSK pain in children presenting to primary care in a Spanish study was trauma representing almost 44% of the presentations with mechanical causes/overuse being the next frequent at 24% . Transient synovitis and inflammatory arthritis accounted for 2.5% and 0.8%, respectively.

The list of diagnoses presenting with MSK pain is large ( Table 1 ). Many of these conditions are discussed in further detail later in this review. A more practical approach categorises diagnoses by patient age and anatomical distribution, whether generalised or localised to one or a few joints ( Table 2 ). The chronicity of pain also assists with diagnosis: acute onset is likely to be associated with trauma; subacute with infection, mechanical (e.g., osteochondroses) or orthopaedic (e.g., slipped upper femoral epiphysis (SUFE)) causes; and chronic with malignancy, inflammation or non-inflammatory pain syndromes . Fig. 1 provides an approach to the main diagnoses of joint pain in children with suggestions for investigations.

Diagnostic approach to a child with joint pains . Note that not all possible diagnoses are shown and that there are always exceptions to the typical presentations of each disease. ASOT, anti-streptolysin O titre; CRP, C-reactive protein; CRPS, complex regional pain syndrome; DDH, developmental dysplasia of the hip; ESR, erythrocyte sedimentation rate; FBC, full blood count; JIA, juvenile idiopathic arthritis; LDH, lactate dehydrogenase; MRI, magnetic resonance imaging; sJIA, systemic juvenile idiopathic arthritis; SLE, systemic lupus erythematosus; SUFE, slipped upper femoral epiphysis; US, ultrasound.

The clinical approach

When faced with a child with joint pains in primary care, initial consideration of the range of differential diagnoses will drive the appropriate history and examination. Although comparatively uncommon, several diseases presenting with MSK symptoms can lead to mortality and long-term morbidity; therefore, they should be actively considered and excluded. These include primary and secondary malignancies, septic arthritis, osteomyelitis, inflammatory arthritis and non-accidental injury/child abuse. Only one in 10,000 children have MSK pain as the primary presenting feature of cancer , although around 20% of children with leukaemia and 2% of those with lymphoma have some MSK symptoms at diagnosis . By far, the most common cause for MSK pain in children presenting to primary care in a Spanish study was trauma representing almost 44% of the presentations with mechanical causes/overuse being the next frequent at 24% . Transient synovitis and inflammatory arthritis accounted for 2.5% and 0.8%, respectively.

The list of diagnoses presenting with MSK pain is large ( Table 1 ). Many of these conditions are discussed in further detail later in this review. A more practical approach categorises diagnoses by patient age and anatomical distribution, whether generalised or localised to one or a few joints ( Table 2 ). The chronicity of pain also assists with diagnosis: acute onset is likely to be associated with trauma; subacute with infection, mechanical (e.g., osteochondroses) or orthopaedic (e.g., slipped upper femoral epiphysis (SUFE)) causes; and chronic with malignancy, inflammation or non-inflammatory pain syndromes . Fig. 1 provides an approach to the main diagnoses of joint pain in children with suggestions for investigations.

Diagnostic approach to a child with joint pains . Note that not all possible diagnoses are shown and that there are always exceptions to the typical presentations of each disease. ASOT, anti-streptolysin O titre; CRP, C-reactive protein; CRPS, complex regional pain syndrome; DDH, developmental dysplasia of the hip; ESR, erythrocyte sedimentation rate; FBC, full blood count; JIA, juvenile idiopathic arthritis; LDH, lactate dehydrogenase; MRI, magnetic resonance imaging; sJIA, systemic juvenile idiopathic arthritis; SLE, systemic lupus erythematosus; SUFE, slipped upper femoral epiphysis; US, ultrasound.

History taking

It is a widely believed aphorism that a physician should ‘listen to the patient and he or she will tell you the diagnosis’ . The history is the key for appropriate management of children with joint pains. With the differentials in mind, a structured history will normally point to one or a few diagnoses, which can be confirmed on examination or simple investigations. The history of the presenting complaint focusses on the pain, eliciting features summarised in the acronym SOCRATES (site, onset, character, radiation, associated symptoms, time course, exacerbating/relieving factors and severity). Young children are often unable to localise pain accurately, and it may not manifest in the typical way with complaints of ‘it hurts’. Limp, reluctance to weight-bear or apparent regression of skills, for example, a toddler who returns to crawling or wanting to be carried, may all be presentations of MSK pain.

When considering site and radiation, pain in a single focal area versus bilateral symmetrical versus generalised can help narrow the differentials (see Table 2 ). Practitioners must beware of referred pain, for example, a patient complaining of knee pain but with underlying hip pathology, in order for conditions such as SUFE not to be missed . Regarding the onset of pain, a clear history of acute injury will often give the diagnosis; however, in the context of a more chronic course, the history of trauma may be incidental to the actual diagnosis of inflammatory arthritis or malignancy .

A key dichotomy for primary care physicians to appreciate is the distinction between inflammatory and non-inflammatory joint pains, which helps with decisions regarding investigation and referral. Joint pain and stiffness, which is worse on rising in the morning and after periods of sitting, and eases with activity, particularly when associated with persistent joint swelling, are indicative of an inflammatory aetiology . Pain that is worse during activity and improves on rest suggests a non-inflammatory cause. However, the latter can be associated with mild temporary joint swelling and aching the morning after an active day; therefore, distinguishing inflammatory from non-inflammatory causes is not always straightforward. One study has highlighted that isolated MSK pain in the absence of other symptoms is very unlikely to be the presenting complaint of juvenile idiopathic arthritis (JIA) or other chronic inflammatory disease . Of 111 patients with isolated MSK pain, only one had a rheumatological condition whereas 64 (84%) of 76 children ultimately diagnosed with JIA did not include pain at all in the presenting symptoms.

A primary care assessment of joint pain should have a high sensitivity for detection of conditions with the risk of mortality or long-term morbidity so that appropriate referral to secondary care can be expedited. Table 3 summarises features (‘red flags’) in the history that can be used to distinguish benign from potentially serious conditions, although there can always be exceptions . Whenever a child is assessed, the possibility of non-accidental injury must be considered. Key features include delay in presentation; absence of, or variation in, the history to explain the injury; a mechanism incompatible with the child’s developmental age; and frequent injury or bruising of different ages .

The past medical history may highlight a preceding upper respiratory tract infection, which can trigger a transient synovitis of the hip in a toddler or a sore throat, and genitourinary or gastrointestinal infection, which may predate reactive arthritis . Caution is warranted, however, given the effect of recall bias and the high prevalence of viral infections in the childhood population, indicating that such reports may be incidental . A prolonged course of systemic corticosteroids in the drug history can predispose to osteoporosis and an increased risk of fracture. A family history is important, particularly of inflammatory or autoimmune conditions such as psoriasis, spondyloarthropathy, inflammatory bowel disease and other HLA-B27-associated diseases. The psychosocial history aids understanding of the impact of the pain on the child’s life and the family’s coping strategies . Particularly in cases of chronic non-inflammatory pain and complex regional pain syndrome, maladaptive family responses may exacerbate and perpetuate the pain . Details of travel and infectious contacts may raise the suspicion of Lyme disease arthritis or tuberculous arthritis.

MSK examination in children

Research has shown that confidence in MSK examination in children is low among both general practitioners and paediatricians . The skills have not been routinely taught to medical students or paediatricians in training ; however, increasing numbers of medical schools are including paediatric MSK assessment in their curricula . Since 2012, the clinical examination of the Membership of the Royal College of Paediatrics and Child Health (MRCPCH) in the UK has included an MSK station. Examination, investigation and management of MSK pathology also form a part of the Diploma of Child Health (DCH) clinical examination syllabus. The DCH examination is taken by around 500 candidates each year, and it is aimed at primary care physicians and doctors who work in specialities with frequent exposure to paediatrics (RCPCH data).

As discussed previously, joint pains may be the presenting feature of diseases that originate outside the MSK system, such as leukaemia, or part of multisystem diseases such as systemic juvenile idiopathic arthritis (sJIA) or systemic lupus erythematosus (SLE). A full systemic examination should therefore be considered, particularly in those with ‘red flags’ for serious or systemic disease in the history. This would include assessing the skin for pallor, rashes or bruising, lymphadenopathy, hepatosplenomegaly and neurological examination, including muscle bulk and strength. Characteristic rashes associated with MSK pains include the following: Gottron papules and heliotrope rash in dermatomyositis, salmon-pink macules in sJIA, malar rash and photosensitivity in SLE, palmoplantar pustulosis in chronic recurrent multifocal osteomyelitis (CRMO) and café-au-lait spots in McCune–Albright syndrome .

A simple and quick screening examination of the MSK system in children based on the adult Gait, Arms, Legs and Spine (GALS) has been developed, and it is called paediatric GALS (pGALS) . This is increasingly being taught at medical schools, and it has been shown to be practicable and accepted by families in developed and developing countries . It is recommended as the initial assessment in any child with MSK symptoms in the history; children who are unwell with pyrexia, with delay or regression of motor milestones, and are ‘clumsy’ in the absence of neurological disease; and those with a chronic disease with known association with MSK presentations . A video of the full examination is available to view on the Arthritis Research UK website . Any area highlighted as abnormal by pGALS should be examined in more detail using paediatric regional examination of the musculoskeletal system (pREMS) . Several review articles provide detailed explanation of examination of the back , hip , knee , foot and ankle . Further practical guides are available on the Paediatric Musculoskeletal Matters website .

The diagnosis of inflammatory arthritis can be made based on examination alone. Key features include swelling of the joint with or without effusion, warmth, joint line tenderness, pain and/or restriction of movement, although not all may be present. Children often deny pain verbally when examined; therefore, the physician should pay close attention to the child’s face to detect grimaces and note involuntary flinching when a joint is passively moved. Young people with hip inflammation often localise pain to the groin, although it may be referred to the thigh or knee . Arthritis tends to affect certain movements before others, and the following features are most sensitive: loss of internal rotation at the hip, hyperextension of the knee and extension of the cervical spine.

Investigations and referral

When should I refer and with what baseline investigations?

Clinical suspicion of the following diagnoses warrant referral to secondary paediatric care (paediatric emergency department or orthopaedics) on the same day without delay incurred by performing investigations in primary care: septic arthritis, osteomyelitis, fractures, non-accidental injury and SUFE. In view of the potentially serious consequences of missing any of these diagnoses, a low threshold for referral is recommended. Further details about the investigation and management of some of these conditions are discussed later in the article. If malignancy is considered possible, discussion with secondary paediatric care and subsequently paediatric oncology/haematology should take place the same day with a view to arranging admission for investigation. These would include bone marrow aspiration for haematological malignancy and CT or MRI for bone and soft tissue tumours.

If clinical assessment suggests an inflammatory condition and the child is systemically well, referral to paediatric rheumatology is most appropriate with outpatient review within 1–2 weeks. Table 4 lists screening questions that may help to prompt appropriate referral . JIA is a common cause for arthritis in children (prevalence one in 1000), and it is diagnosed clinically as discussed in detail later. Although the classification criteria for JIA specify the persistence of joint inflammation for at least 6 weeks , in order to avoid undue delay, it is reasonable for referral from primary care to paediatric rheumatology to be made after 3–4 weeks of symptoms or signs. The British Society for Paediatric and Adolescent Rheumatology have written Standards of Care for JIA, which recommend review by the paediatric rheumatology team of all children and young people with suspected JIA within 10 weeks of onset of symptoms and 4 weeks of referral .

Table 4

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