Sinding-Larsen-Johansson Syndrome
Description
Sinding-Larsen-Johansson syndrome is an irritation of the growth area at the bottom tip of the kneecap, where the kneecap tendon begins. It is a close cousin of Osgood-Schlatter — the same problem, one notch higher — and is sometimes called the growing child’s version of “jumper’s knee.”
How it happens (the mechanism)
Bones grow at special zones called growth plates. The main one, the physis, is what makes a bone longer. There is a second kind, called an apophysis — a growth center at a bony bump where a tendon anchors muscle to bone. The lower tip of the kneecap — where the quadriceps (thigh muscle), through the kneecap, gives rise to the kneecap tendon — carries one of these apophyses.
While a child is still growing, that apophysis is made of cartilage, not yet hardened into bone. Cartilage — the same rubbery material as in the ear or the tip of the nose — is softer than bone and weaker under tension. So when its muscle pulls hard or often, the apophysis is the part that complains.
During a growth spurt, the bones lengthen faster than the muscles can keep up, so the muscles become relatively tight and tug harder on the apophysis. Here, a tight quadriceps pulls on the lower pole of the kneecap with every jump and sprint. Day after day, that extra, sustained tension irritates and inflames the growth center — essentially the growing child’s version of the insertional tendinitis adults get where a tendon meets bone. The pain is inflammatory and can be surprisingly sharp. (In an older teen, a single explosive effort can occasionally pull the apophysis off as an avulsion fracture; the everyday version is this inflammation.)
Symptoms
Pain and tenderness right at the lower tip of the kneecap, worse with running, jumping, kneeling, and stairs and better with rest, sometimes with mild local swelling. It tends to affect active children during growth spurts.
Doctor examination and imaging
It is diagnosed from the exam — tenderness at the lower pole of the kneecap. X-rays are not usually needed but may be used to rule out other causes.
Treatment
As with Osgood-Schlatter, anti-inflammatory measures and ice give relief, but the lasting fix is daily stretching of the quadriceps to take tension off the apophysis. Activity is safe as tolerated, easing off only when pain is limiting. Surgery is not needed.
Recovery and long-term outlook
It is self-limiting and resolves as the growth area matures, with no lasting harm to the knee.
When to call the doctor
Call if pain is severe or worsening, your child will not bear weight or use the leg at all, the area becomes very swollen, red, or warm, your child develops a fever, or things are not improving with rest as expected.
Learn more
OrthoInfo (AAOS) — Osgood-Schlatter Disease: orthoinfo.aaos.org
This information is for educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. For specific concerns about your child, consult a board-certified, fellowship-trained pediatric orthopaedic surgeon.