Sinding-Larsen-Johansson syndrome is irritation and inflammation of the growth plate (apophysis) at the bottom of the kneecap (patella) where the patellar tendon inserts. In a child, the bones grow from areas called growth plates. The growth plate is made up of cartilage cells, which are softer and more vulnerable to injury than mature bone. Sinding-Larsen-Johansson is most often seen in children between the ages of 10 and 15 and usually appears during a period of rapid growth.
Sinding-Larsen-Johansson syndrome is caused by increased tension and pressure on the growth center. This pressure usually results from overuse of the knee (repetitive running and jumping). Having tight quadriceps muscles (in the front of the thigh) also puts pressure on this growth center and may make this condition more likely to occur. Tight muscles are more common during a growth spurt.
Your child will complain of a pain at the bottom of the kneecap. He may have swelling at this location, and the pain may limit his activities.
Your doctor will do a physical examination of the knee and review your child's symptoms. X-rays may show irregular bone edges or fragments at the bottom end of the kneecap, but are not generally required to make the diagnosis.
Your child will need rest from painful activities in order to take the pressure off the growth center and allow the inflammation to resolve. Ice packs should be applied to the knee for 15-20 minutes every 2-4 hours for 2-3 days or until the pain goes away. Your child's doctor may prescribe a strap to support the kneecap and recommend stretches for tight muscles.
Returning to Activities & Sports
The goal is to return your child to his sport as quickly and safely as possible. If he returns to sports or activities too soon, or pushes through pain, the injury may worsen, which could lead to chronic pain and difficulty with sports. Everyone recovers from injuries at different rates. Return to sports or activities will be determined by how soon your child's knee recovers, not by how many days or weeks it has been since the injury occurred.
Your child may return safely to sports or activities when each of the following is true (Begin at the top of the list and progress to the bottom):
- His lower kneecap is no longer tender and swollen
- The injured knee can be fully straightened and bent without pain
- The knee and leg have regained normal strength compared to the uninjured knee and leg
- He is able to jog straight ahead without limping
- He is able to sprint straight ahead without limping
- He is able to do 45-degree cuts.
- He is able to do 90-degree cuts
- He is able to do 20-yard figure-of-eight runs
- He is able to do 10-yard figure-of-eight runs
- He is able to jump on both legs without pain and hop on the injured leg without pain
Limit Activity with Pain
The most important thing to do is to have your child limit activity as soon as he notices the pain at the bottom of the kneecap. Warming up before activity and quadriceps stretching after activity may also help to prevent Sinding-Larsen-Johansson syndrome.
Ten minutes of light jogging or cycling before practice will increase circulation to cold muscles, making them more pliable and less prone to strain or rupture. Studies have shown that an active warm-up is associated with better athletic performance than a warm-up that consists only of static stretching.
Tight muscles are more prone to injury. Tight muscles also put more stress on the attached tendons and bones, putting these tissues at risk for injury as well. Regular stretching can improve muscle flexibility. The ideal time to stretch is after your workout. Include all major muscle groups. Don't bounce. Hold each stretch for 20-30 seconds.