Limb pains, especially leg pains in children, are a common presenting symptom in general practice. It can be difficult to diagnose a specific cause and many children undergo unnecessary tests, with the diagnosis often being ‘growing pains’ because no specific abnormality is found.
Among paediatric rheumatologists, consensus is developing that growing pains are often the result of hypermobility. We now recognise that a child diagnosed with growing pains usually has benign joint hypermobility syndrome, which, unlike growing pains, can be helped.
It is important to develop a logical approach to limb pain. There are three main categories to consider. The first, a red flag, is recurrent limb pains waking the child every night, with pain in the same limb and the same part of the limb.
This is often the first sign of a bone tumour; some are benign, but some, such as Ewing’s sarcoma, are malignant.
In the history, the GP should first find out if the pain occurs daily, particularly waking the child at night and always on the same side. Once this has been excluded, other causes of limb pain can be divided into inflammatory or mechanical, with the majority in the latter group.
Inflammatory joint pains tend to have been present for a shorter time, often weeks, whereas mechanical problems quite often have a long, intermittent history, sometimes over years.
For a diagnosis of juvenile idiopathic arthritis (formerly known as chronic inflammatory arthritis of childhood), the joints have to be actively swollen, warm or restricted for a minimum of six weeks.
Mechanical problems tend to be intermittent and usually worse after exercise and in the evenings. In hypermobility syndrome,there is often a history of gastrooesophageal reflux as a baby, constipation, headaches due to trapezius and temporalis muscle spasm, abdominal pain due to colon spasm and easy bruising due to skin elasticity. These symptoms are commonly seen together with limb pains.
The child may have difficulty writing, with associated hand pain and messy handwriting. Children often complain of tiredness and like to be carried or go in the buggy. They fatigue easily, especially with long walks.
Inflammatory problems tend to cause early morning stiffness lasting more than 15 minutes, which improves over the day. Joint swelling may be noted with inflammatory problems, but this is not reliable and parents often report that joints are swollen when they are not. Some parents may have noted heat from the affected joint in arthritis.
One should ask about preceding infections, because a reactive arthritis after a viral or streptococcal infection is quite common.
Examination of the musculoskeletal system should be aimed at examining all the joints because arthritis is not always painful and the child may not have complained about certain joints.
Starting with neck movements in particular, assess neck extension by asking the child to look up. This is limited by arthritis. Look for trapezius muscle spasm, which is common in hypermobility and causes neck stiffness and headaches. Shoulder movement in abduction is increased in hypermobility and decreased in shoulder arthritis. The elbows hyperextend in hypermobility, usually by more than 10°. Arthritis causes fixed flexion deformities of the elbow. Wrists will not dorsiflex if arthritis is present and swelling is easy to feel in the wrist. The fingers at the metacarpophalangeal joints hyperextend in hypermobility and the thumb with the wrist flexed can often touch the forearm.
Hips abduct 90° in hypermobility, but in arthritis, internal rotation of the hip is restricted.
In arthritis, the knees are swollen with fixed flexion and heat is felt, whereas in hypermobility, they hyperextend.
Swelling of ankles is best seen from behind the ankle by the Achilles tendon. Hypermobility is usually associated with flat, pronated feet. Muscle strength, particularly in specific muscles, such as hip abductors, is weak in hypermobility.
Hypermobility is usually differentiated from arthritis on the history and examination. If the diagnosis is hypermobility, no further investigations are needed.
Treatment of hypermobility involves physiotherapy by a therapist who understands related problems, such as muscle weakness, and works to build strength and stamina. Occupational therapy, podiatry and osteopathy can also be beneficial.
If the child has arthritis, a connective tissue screen is justified, including FBC and film to rule out leukaemia and other haematological problems, ESR and CRP to see if there are increased inflammatory markers, rheumatoid factor (only 3% of childhood arthritis is rheumatoid factor positive) and antinuclear antibody (associated with oligo-articular juvenile idiopathic arthritis and uveitis). NSAIDs can be used, but referral to a paediatrician or paediatric rheumatologist is justified for definitive treatment, such as intra-articular steroid injections, steroids and methotrexate for more severe cases.
- Dr Nathan Hasson is a consultant paediatrician in rheumatology at The Portland Hospitalin London