Juvenile idiopathic arthritis (JIA) may either speed or slow the natural growth process of the bones on either side of the affected joint, causing uneven bone growth. Children who have JIA may not grow as tall as they would have if they did not have the condition. The growth differences depend on the child's age when the disease started and the number of joints affected. The more joints involved in the disease, the more severe the impairment.
- Leg length: Different leg lengths are a possible complication if arthritis affects only one knee. The leg that is affected by arthritis may not grow at the same rate as the other leg. So it may be shorter or longer than the unaffected leg.
- Jaw development: If JIA affects the jaw (temporomandibular) joint, it may cause one or both sides of the lower jawbone to grow more slowly than normal. If the lower jaw does not develop normally, it can lead to difficulty eating. In some cases surgery is needed to restore a more normal jaw function and appearance.