Sinding-Larsen-Johansson syndrome is swelling and irritation of the growth plate in the kneecap (patella). Growth plates are layers of cartilage near the ends of bones where most bone growth happens.

Kids with Sinding-Larsen-Johansson syndrome have knee pain, especially when running, jumping, and walking up or down stairs. They may have knee swelling and stiffness. Healing can take a few months, but most kids don't have any lasting problems.

Activity

• Your child needs to rest the knee. Often this means taking time off from sports that involve a lot of running and jumping. Going back to these sports too soon could cause a fracture (break) in the kneecap. Low-impact sports like swimming and walking are usually OK.
• When your health care provider says it's OK, your child can gradually increase activities. If they have no pain, they can continue to add more activities and training.
• If an activity causes pain or swelling, your child should stop doing it and put ice wrapped in a towel on the knee for about 20 minutes. They can try the activity again after the knee stops hurting or switch to a less intense activity.

To help with pain and swelling:

• Give your child acetaminophen (Tylenol^® or a store brand), ibuprofen (Advil^®, Motrin^®, or a store brand), OR naproxen (Aleve^®, Naprosyn^®, or a store brand) as needed for pain. Follow the directions on the label for how much to give and how often.
• Place ice wrapped in a towel on the knee for about 20 minutes several times a day. Do not put ice directly on the skin.
• Wrap the knee in an elastic bandage. 

Follow your health care provider's advice for:

• whether your child needs to wear a knee immobilizer to keep the knee still
• any movement exercises or stretches your child should do and any activities to avoid
• whether your child should go to a bone doctor (orthopedist), sports medicine doctor, or physical therapist to help them build strength and flexibility and create a plan for returning to full activities and sports
• when your child can return to sports. Usually, this is when your child has no pain or swelling during or after the activity.
• any protective gear (such as knee pads) that your child should wear when they return to sports
• when your child should follow up

• Your child has pain that doesn't get better after following the health care provider's instructions.
• You're not sure which activities your child should do.
• Your child has finished growing and still has knee pain or swelling.

What causes Sinding-Larsen-Johansson syndrome? Sinding-Larsen-Johansson syndrome usually happens during the growth spurt of puberty (9–14 years old) when bones, muscles, and tendons grow at different rates. The tendons can get tight, and when someone does sports that involve a lot of running and jumping (like basketball and soccer), they can pull on and injure the growth plate in the kneecap. It's more common in boys but also can happen in girls.

What can help prevent Sinding-Larsen-Johansson syndrome from coming back? It can help for your child to:

• Make sure they increase the length and intensity of their workouts slowly.
• Do different sports and activities so that they strengthen different muscle groups. 
• Stretch before and after activity and sports.
• Wear shock-absorbing insoles in their sneakers and cleats. 
• Place ice wrapped in a towel on the knee for about 20 minutes after activity and sports. Do not put ice directly on the skin.
• Lose weight (if overweight).