What Is Sinding Larsen Johansson Syndrome?

  • Tristan Derry MBBS Medicine - Bart’s and the London School of Medicine and Dentistry

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Sinding Larsen Johansson syndrome (SLJS) occurs when there is damage to the growth plate where your kneecap attaches to the patellar tendon, causing pain during physical activity. It’s a common cause of knee pain in children and teenagers who frequently play sports.

Read on to learn more about the anatomy of the knee, and how specific mechanisms contribute to the development of SLJS. This should help you differentiate this condition from other knee pains.

Anatomy of the knee

The knee is the largest joint in the body and is comprised of the thigh bone (femur), the shin bone (tibia), and the kneecap (patella). The muscles around this joint, like the quadriceps and the hamstrings, attach to these bones via tendons. Think of tendons as thick, strong rubber bands, that allow the muscles to contract and relax, providing us with movement.

What goes wrong in SLJS?

In some children, the areas in which the bone grows, called the growth plate, can be disrupted. This is usually due to too much exercise, which puts a lot of strain on the muscles and the tendons around the knee joint.

In SLJS, tension and straining through the patellar tendon, one of these ‘thick rubber bands’, through repeated exercise will irritate the growth plate. This causes a small part of the bone to protrude on the lower part of the kneecap. This small protrusion will then rub against the patellar tendon, irritating the tendon and causing pain in the knee.1


  • Pain and swelling below the kneecap
  • One or both knees can be affected
  • Pain when kneeling
  • Pain increases with physical exercise, especially activities that put more force through the knee joint
  • Bony prominence at the bottom of the kneecap (patella)

It’s important to note that SLJS can affect one or both knees, and the level of pain may fluctuate.

Who does it affect?

SLJS primarily affects children and teenagers aged 10 – 14 years old, who play sports such as football, rugby, running and gymnastics. This is because these sports put a lot of strain on the knee joint, particularly the patellar tendon.

What else could it be?

There are a few conditions similar to SLJS, such as Osgood-Schlatter’s Syndrome and Patellar tendinopathy, which is commonly referred to as ‘jumper’s knee’. Both these conditions will present with similar symptoms, as the pain will also be just below the kneecap.


The clinician will likely have a look at your child’s knees and shins by performing a physical examination. The examination will involve your child performing some movements, and the clinician feeling around the joint for any swelling or pain.

If they suspect it could be SLJS, they will request a form of radiological imaging, such as an X-ray, Magnetic Resonance Imaging (MRI), or an ultrasound. These scans will help rule out any other conditions or injuries and confirm their diagnosis.

Treatment and management

SLJS is referred to as a self-limiting condition, meaning that most of the time, it will get better on its own.


Therefore, the clinician will advise your child to take a break from playing sports for some time to allow the patellar tendon to recover. Most children will need to take a few weeks to months off from sports. It may be possible to replace this exercise with sports that place less stress on the knee, such as swimming.

Physiotherapy can also be recommended, as this will help strengthen the muscles around the joint, helping the tendon heal and prevent a similar episode in the future. They can also give guidance on particular stretches your child can do to reduce the tension in their muscles. 


If the pain is bad, they may advise you to take the recommended dose of a non-steroidal anti-inflammatory drug (NSAID), such as ibuprofen or aspirin. These will reduce the pain, as well as reduce swelling and inflammation around the tendon.


In most cases, it is very unlikely that your child will require surgery. However, in severe cases where some of the bone is fractured, this may be the most appropriate treatment.

When will my child feel better?

Full recovery can take up to 12 months, but your child should start feeling better once the NSAIDs have kicked in. It’s important to note that this doesn’t mean the patellar tendon has healed, so taking a break from sports to allow it to heal will be the most important factor in their recovery. While NSAIDs can provide relief from pain and inflammation, the true healing process requires patience and a gradual return to physical activity.

What questions should you ask your doctor?

Here are a few questions you can ask to ensure your child has the best recovery possible:

  • How long should my child refrain from playing sports?
  • Which stretches can reduce the risk of developing SLJS again?
  • Will my child need any scans or tests?
  • Is this SLJS or Osgood-Schlatter disease?


To prevent Sinding-Larsen-Johansson Syndrome (SLJS), a proactive approach addressing the underlying factors contributing to its development is essential. Implementing the following strategies can significantly reduce the risk of SLJS and promote overall knee health.

Structured training programs

Encourage children and teenagers to engage in sports with well-designed training programs. These programs should incorporate a proper warm-up, stretching, and cool-down routines, emphasising gradual progression in intensity and duration. This approach allows the musculoskeletal system to adapt without subjecting the knee joint to excessive stress.

Diversification of sports activities

Advocate for a diverse range of physical activities to avoid over-specialisation in a single sport. Over-specialisation can lead to repetitive stress on specific joints, including the knee. Encouraging a well-rounded sports portfolio helps distribute the load on the knee more evenly.

Balanced rest and activity

Emphasise the importance of incorporating sufficient rest periods between training sessions and competitive events. Continuous, high-intensity training without appropriate breaks can increase the risk of overuse injuries. Providing adequate time for the body, especially the knee joint, to recover is crucial.

Protective equipment

Ensure the consistent use of appropriate protective equipment, such as well-fitted footwear and knee support, particularly in high-impact sports. This gear provides support and helps minimise stress on the patellar tendon, offering an additional layer of defence against injuries.


Following a stretching regime can help with your child’s recovery by improving muscle flexibility.

A quadriceps stretch, which focuses on the large thigh muscle on the front, will reduce the tension on the knee joint. Start by lying on your front. Then, using a band or long towel around your ankle, pull your heel towards your buttocks. You should feel a stretch in your thigh muscles. Hold this position for about 20 seconds, repeating it 3-4 times on each leg.

Performing a hamstring stretch focuses on the muscles at the back of your thigh. Sitting on the floor with your legs straight, try to reach forward, attempting to touch your toes. It’s important that the knee is kept straight whilst doing this. Hold for about 20 seconds, repeating 3-4 times on each leg.


Sinding-Larsen-Johansson Syndrome (SLJS) is a common cause of knee pain in active children and teenagers, occurring when the growth plate, where the kneecap attaches to the patellar tendon, is damaged. This condition, often linked to excessive exercise, leads to a protrusion in the bone, causing pain and irritation in the knee. The symptoms include pain, swelling, and discomfort during physical activities, particularly those that exert force on the knee joint.

SLJS is often self-limiting, requiring rest from sports for weeks to months. Physiotherapy strengthens muscles around the joint, aiding in recovery. Medications like NSAIDs alleviate pain, and surgery is rarely needed.

Full recovery may take up to 12 months, emphasising the importance of patience, rest, and a gradual return to physical activity for healing the patellar tendon.


  1. Negrão E, van den Eede E, Kyriazopoulos A, Romijn MG. Sinding-Larsen-Johansson syndrome with minimally displaced patellar sleeve avulsion fracture: a case report with multimodality approach and literature review. Skeletal Radiology [Internet]. 2022 Nov 17 [cited 2023 Jan 17]; Available from: https://pubmed.ncbi.nlm.nih.gov/36396893/
  2. Sinding-Larsen-Johansson syndrome [Internet]. Cambridge University Hospitals. Available from: https://www.cuh.nhs.uk/patient-information/sinding-larsen-johansson-syndrome/
  3. Sinding-Larsen-Johansson Syndrome: Diagnosis & Treatment [Internet]. Cleveland Clinic. [cited 2023 Nov 16]. Available from: https://my.clevelandclinic.org/health/diseases/22530-sinding-larsen-johansson-slj-syndrome#management-and-treatment

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This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Tristan Derry

MBBS Medicine - Bart’s and the London School of Medicine and Dentistry

Tristan is a dedicated medical student driven by a passion for health tech communications. Seamlessly blending his medical knowledge with his experience as a copywriter, he strives to educate patient's about their medical conditions.

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