Sinding-Larsen-Johansson syndrome is an overuse injury of the growth area at the bottom tip of the kneecap, where the patellar tendon attaches. It affects active children, usually between the ages of 10 and 14, and causes pain just below the kneecap with running, jumping and kneeling. It is closely related to Osgood-Schlatter disease, which affects the other end of the same tendon, and it settles by itself as the bone matures, usually within a year.
Also known as SLJ syndrome, jumper's knee in children, inferior pole patellar apophysitis
Anatomy: where the problem is
Front view of the knee. Highlighted in the diagram: lower tip of the kneecap.
Symptoms
- Pain at the lower tip of the kneecap
- Pain that is worse with running, jumping, climbing stairs, squatting and kneeling
- Tenderness when pressing on the bottom of the kneecap
- Mild swelling just below the kneecap
- Tight thigh muscles
- Pain that eases with rest and returns with sport
Causes and risk factors
- Repeated pull of the patellar tendon on a growth area that is not yet fully formed
- A growth spurt, when bones lengthen faster than muscles adapt
- Sports with a lot of jumping, sprinting and kicking, such as football, basketball, netball, gymnastics and athletics
- Training or playing on many days a week without enough rest
- Tight thigh and calf muscles
What the evidence says helps
- It is a self-limiting condition. The original description of its natural history found that it resolves as the kneecap matures, typically over 3 to 12 months.1
- Treatment is managing load: reducing the amount of running and jumping to a level that keeps pain mild, without stopping activity altogether.2
- Pain during sport in a child is a warning sign of overload and should lead to activity being modified, not ignored.2
- A sports medicine position statement recommends limiting weekly training hours, building in rest and avoiding early specialisation in one sport to reduce overuse injuries in young athletes.3
- An X-ray is not usually needed, but it may be arranged if the pain followed a single injury or does not behave as expected.1
Things you can try at home
- Cut back on running and jumping until pain during and after sport is mild
- Keep your child active in ways that do not hurt, such as swimming or cycling
- Use ice after activity if it helps
- Stretch the thigh and calf muscles gently, and build leg strength as pain allows
- Tell coaches and PE teachers, so that training can be adapted
- Increase activity again gradually as the pain settles
When to get urgent help
Contact your GP urgently, call NHS 111, or call 999 in an emergency if you have:
- A child who cannot put weight on the leg, or has a limp with no clear cause: see a GP the same day
- A hot, red, swollen joint, or pain with a fever or feeling unwell: get same-day medical help
- Pain that wakes your child at night, or pain at rest that is not linked to activity: see your GP
- Pain with unexplained weight loss, tiredness, bruising or a lump: see your GP promptly
- Sudden severe pain at the kneecap during a jump or sprint, with swelling or difficulty straightening the knee: go to A&E
How Apollo can help
We examine the knee and hips and ask about your child's sport, training and growth. If the findings fit, we explain what is happening and reassure you both that it will settle with time. We then agree how much activity is sensible for now, show your child stretches and strengthening exercises, and plan a gradual return to full training, liaising with coaches if that helps. If the pain does not behave as expected, we ask your GP to arrange further checks.
No GP referral needed. Clinics in Sheringham, Coltishall and Norwich.
Related reading
Frequently asked questions
Is Sinding-Larsen-Johansson syndrome the same as Osgood-Schlatter disease?
They are closely related. Both are overuse injuries of a growth area at one end of the patellar tendon. Sinding-Larsen-Johansson affects the bottom of the kneecap, and Osgood-Schlatter affects the bump at the top of the shin bone. They are managed in the same way.
Does my child have to stop sport?
Usually not completely. The aim is to reduce running and jumping enough to keep pain mild, and to keep them active in other ways. A short period of complete rest from sport is sometimes needed if the pain is severe.
How long does it last?
Most children recover within 3 to 12 months. Symptoms can come and go during growth spurts, and they stop once the growth area at the bottom of the kneecap has matured.
References
- Medlar RC, Lyne ED (1978). Sinding-Larsen-Johansson disease. Its etiology and natural history. The Journal of Bone & Joint Surgery 60:1113-1116. View source
- Launay F (2015). Sports-related overuse injuries in children. Orthopaedics & Traumatology: Surgery & Research 101:S139-S147. View source
- DiFiori JP, et al. (2014). Overuse injuries and burnout in youth sports: a position statement from the American Medical Society for Sports Medicine. British Journal of Sports Medicine 48:287-288. View source
This page is general information, not a diagnosis or a substitute for medical advice. If you are worried about your symptoms, speak to your GP or a registered healthcare professional. Content prepared from the sources above, November 2026.
