A number of conditions can cause painful, stiff joints in children. Juvenile idiopathic arthritis (JIA) is a relatively uncommon cause of these symptoms. Most often, joint pain can be linked to an injury.

Other conditions that may be confused with JIA include:

• Growing pains.
• Injury or overuse (knee pain, bursitis, tendinitis).
• Other inflammatory diseases, including lupus, rheumatic fever, or other types of arthritis.
• Hypermobility syndrome ("double-jointed"), which can cause joint pain at night and after heavy or unusual activity. The child may show unusual ability to overextend or overstraighten the knees, fingers, hands, or elbows.
• Lyme disease.
• Inflammation in a joint caused by a foreign body, such as a splinter in the joint.
• A condition in which the upper end of the thighbone slips off the rest of the bone (slipped capital femoral epiphysis).
• A tumor.
• Infection of a joint (bacterial or septic arthritis).
• Infection of a bone (osteomyelitis).
• Arthritis associated with inflammatory bowel disease.
• Other diseases that affect cell growth, such as leukemia.