Sinding-Larsen-Johansson (SLJ) syndrome is pain at the bottom of the kneecap (patella). It is caused by swelling and irritation of the growth plate there. A growth plate is a layer of cartilage near the end of a bone where most of the bone's growth happens. It is weaker and more at risk for injury than the rest of the bone.
SLJ syndrome goes away when a teen is done growing and usually doesn't cause lasting problems.
What Are the Symptoms of Sinding-Larsen-Johansson Syndrome?
SLJ syndrome typically causes pain near the bottom of the kneecap. A teen also might have:
swelling and tenderness around the kneecap
pain that increases with exercise or activities like running, climbing stairs, or jumping
pain that gets more severe when kneeling or squatting
a swollen or bony bump at the bottom of the kneecap
What Causes Sinding-Larsen-Johansson Syndrome?
Sinding-Larsen-Johansson syndrome is caused by repeated stress on the kneecap growth plate. The patellar tendon connects the kneecap to the shinbone (tibia). Every time the leg is straightened, the patellar tendon puts stress on the growth plate.
Who Gets Sinding-Larsen-Johansson Syndrome?
Sinding-Larsen-Johansson syndrome usually happens in teens who are:
How Is Sinding-Larsen-Johansson Syndrome Diagnosed?
To diagnose SLJ syndrome, health care providers ask about physical activities and do an exam.
Testing usually isn't needed. But sometimes doctors order an X-ray or magnetic resonance imaging (MRI) scan to check for other knee problems.
How Is Sinding-Larsen-Johansson Syndrome Treated?
Someone with SLJ syndrome needs to limit activities that cause so much pain that it's hard to do that activity. For example, if you feel a little pain when running, it's OK to keep running. But if running causes a limp, stop and rest. When the pain is better (usually after a day or two), you can try the activity again.
To keep leg muscles strong and flexible while you get better, your doctor will recommend physical therapy (PT) or a home strengthening and stretching program. It doesn't happen often, but some teens might need to take a break from sports for a few weeks.
To feel more comfortable while healing from SLJ syndrome:
Put ice or a cold pack on the knee every 1–2 hours for 15 minutes at a time. Put a thin towel between the ice and your skin to protect it from the cold.
If your health care provider says it's OK, you can take ibuprofen (Advil, Motrin, or store brand) or acetaminophen (Tylenol or store brand). Follow the directions that come with the medicine for how much to take and how often.
Can I Still Play Sports With SLJ Syndrome?
Teens with SLJ syndrome usually can do their normal activities, including sports, as long as:
The pain is not bad enough to interfere with the activity.
The pain gets better within 1 day with rest.
How Can I Deal With SLJ Syndrome?
SLJ syndrome may come and go until you're done growing (usually mid-to-late teens). To help prevent SLJ syndrome from coming back:
Stop doing an activity if knee pain or swelling comes back. Then, try to limit your activity until the pain or swelling goes away.
If possible, avoid or limit activities that put a lot stress on the knees, such as walking up and down stairs, lifting heavy objects, and squatting.
When exercising or playing sports:
Work with a coach or trainer to make sure you use proper technique.