Today’s Wonder of the Day was inspired by Joshua. Joshua Wonders, “How does Arthritis develop in a child's body?” Thanks for WONDERing with us, Joshua!

Have you ever taken a really long hike through challenging terrain? No, we're not talking about walking around the playground at recess. We're talking about five miles or so on rough trails in the wilderness.

If you've ever been on a tough hike or if you've ran a 5K race, played a 90-minute soccer game, or ice skated for several hours, then you probably know what it feels like to have sore joints and muscles the next day.

The day after strenuous exercise might start with a battle to get out of bed. It can hurt just to bend your arms and legs. Standing up can be accompanied by popping joints, creaks, groans, and moans.

It's natural to feel this way after vigorous exercise, especially if you're not used to a strenuous workout. But what if you felt that way every morning simply because you have a medical condition?

Unfortunately, that's the case for people with arthritis, a disease that causes swelling, stiffness, and pain in a person's joints. Specifically, arthritis consists of inflammation of the synovial membrane that lines the joints.

You may have an older friend or family member who has arthritis. Arthritis is most common among older adults, making movement more difficult and painful as they get older. However, it can also strike children.

The most common type of arthritis experienced by those under the age of 17 is known as juvenile idiopathic arthritis (JIA). You may also hear it referred to as juvenile rheumatoid arthritis (JRA). There are seven types of JIA, depending upon how many and which types of joints are affected.

Doctors still aren't sure what causes JIA. Some believe it may be genetic. It's possible that an environmental factor, such as a virus, could trigger JIA in children genetically predisposed to develop the condition. Fortunately, JIA isn't contagious, so you can't catch it from someone who has it.

JIA is an autoimmune disease, which means the immune system attacks healthy cells rather than germs, such as bacteria and viruses. The chemicals released by the immune system cause the swelling, stiffness, and pain associated with arthritis.

There is no cure for JIA, but it can be treated with medicines that fight pain and inflammation. Physical therapy can also be helpful. Stretching, staying active, and taking warm baths can also help soothe aching joints.

As a chronic condition, JIA can last for several months to many years. Fortunately, many children eventually outgrow JIA with no permanent joint damage as adults. Others may continue to experience problems that require continued treatment as adults.

Wonder What's Next?

I spy with my little eye…tomorrow’s Wonder of the Day!