When a smaller number of joints are affected (the oligoarticular type) there are four or fewer joints exhibiting arthritic symptoms with the larger joints being preferentially affected. Such children do not present as unwell although they may limp when asked to walk. Arthritis may be confined to one hip but if the symptoms are limited to this joint then an alternative diagnosis should be sought as this is much more common, with Perthes disease a typical outcome. Arthritis over some time develops weakness and loss of bulk in the main knee muscles and a knee bend contracture partly due to tightening of the hamstrings. A discrepancy in length of legs can develop if arthritis affects only one leg.

With a larger number of joints affected, a minimum of five or more, the child has the many joint or polyarticular form of arthritis, with typically joints affected on both sides, a so called symmetrical involvement. A mild fever may be present and there can be significant muscle weakness and limitation of normal functioning if the joints have a severe limitation in their ranges of motion. A complete physical examination of the patient is vital to ensure that the diagnosis is juvenile arthritis, in what areas the physical limitations exist and which type of arthritis the patient is suffering from.

The definition of arthritis for the examination is the presence of swelling inside the joint (often called an effusion), along with limited joint motion and perhaps pain, warmth and redness of the joint area. It is not possible to determine swelling of some joints such as the hips but they do exhibit pains and limited ranges of movement. A definitive diagnosis may take time to establish as the arthritis may develop at the same time as the fever and the rash but can occur some months later. The lymph nodes and the liver may be enlarged and muscles may be tender to palpation. In the fewer joint form of juvenile arthritis there is often only one joint affected.

In the polyarticular form of arthritis where many joints are inflamed, it is common for there to be a symmetrical involvement of the weight bearing joints as well as smaller ones of the hand. The joint cartilage may be reduced in thickness with eroded areas and in some joints the formation of a fusion across them. With more chronic changes there can be thickened synovial membranes and joint effusions, subluxations (partial dislocations), joint contractures and stiffness, bony deformity (particularly the fingers) and bony enlargements. The joints can also lose bone mass and suffer narrowing of the joint spaces as the cartilage thins.

A reduction of extension in the neck may not produce any symptoms but it is important to identify this as it can indicate arthritic changes in the cervical spine which can lead to partial dislocation (subluxation) of the upper neck bones, a potentially dangerous situation. The neck bones can also fuse together along the posterior structures. The jaw joints, the tempero-mandibular joints, may also be affected and lead to reduced amount of growth in the lower jaw with inability to open the mouth as wide as normal. There may also be involvement of the eyes in the inflammatory process.

Juvenile arthritis and other complex conditions are best managed by a specialised multidisciplinary team due to the numerous problems which patients have to do with family and patient education and schooling, drug treatments, physiotherapy and occupational therapy. It is rarely if ever successful to give isolated treatments to this patient group. Reviewing patients at regular intervals allows the drug treatments to be fine tuned towards a reduction in the morning stiffness and towards fewer affected joints until no symptomatic joints remain. A typical team to manage these conditions may include a physiotherapist, occupational therapist, social workers, a paediatric rheumatologist and nurse.

These patients do not routinely require surgical care although steroid injections into some joints can be useful. Knee and hip arthritis in polyarticular arthritic patients may be managed by joint replacement once bone growth has ceased at skeletal maturity. Resting for long periods is unhelpful and patients should be encouraged to keep active for a better end result.

Jonathan Blood Smyth, editor of the Physiotherapy Site, writes articles about Physiotherapy, back pain, orthopaedic conditions, neck pain, injury management and Local Croydon Physiotherapists. Jonathan is a superintendant physiotherapist at an NHS hospital in the South-West of the UK.