Sinding-Larsen-Johansson syndrome, often shortened to SLJ syndrome, is a condition that causes pain and tenderness at the bottom of the kneecap in growing children and teenagers. It tends to occur during periods of rapid growth and is particularly common in young athletes involved in sports with lots of running, jumping, kicking or repeated bending of the knee.
The pain comes from the area where the patellar tendon meets the lower tip of the kneecap. While the skeleton is still developing, this area can be more sensitive to repeated stress. When the quadriceps muscles contract during activities such as jumping, running or squatting, they place tension through the patellar tendon and its attachment to the kneecap. If the amount of activity exceeds what the developing area can comfortably tolerate, it can become sore and irritated.
SLJ syndrome is closely related to Osgood-Schlatter disease, but the two conditions affect different locations. Osgood-Schlatter causes pain where the patellar tendon attaches to the shin bone, while SLJ causes pain where the tendon attaches to the bottom of the kneecap.
SLJ syndrome does not usually mean that a child needs to stop sport completely. Instead, treatment is generally about finding the right balance between activity and recovery while the knee is growing. Adjusting aggravating activities, gradually building strength and improving the knee’s tolerance to sporting loads can help young athletes continue participating while keeping symptoms under control.
Key Facts
- SLJ syndrome has been reported to have a 2% to 5% incidence in children aged 10 to 15 years, with jumping sports commonly involved. 🔗
- A published case report of a 13-year-old competitive football player with SLJ syndrome reported complete recovery after five months of avoiding sports activity, with follow-up ultrasound showing no remaining abnormality. 🔗
- Up to 30% of young people with SLJ syndrome may have symptoms in both knees. 🔗
Risk Factors
- Age around early to mid-adolescence, especially during a rapid growth spurt
- Regular participation in jumping, running, kicking or change-of-direction sports
- Sudden increases in training load, such as extra sessions, tournaments, trials or representative sport
- Reduced quadriceps, hip flexor, hamstring or calf flexibility
- Reduced hip, thigh or calf strength for the demands of sport
- Poor landing control, especially knees collapsing inwards or stiff landings
- High weekly sport volume with limited recovery days
- Previous growth-related pain such as Osgood-Schlatter disease or Sever’s disease
- Hard training surfaces or repeated jumping on courts
- Continuing to train through worsening pain
Symptoms
- Pain at the bottom of the kneecap, usually over the lower tip of the patella
- Tenderness when pressing the inferior pole of the patella
- Pain during running, jumping, hopping, sprinting or change-of-direction sport
- Pain with squatting, lunging, stairs or kneeling
- Swelling or puffiness around the lower kneecap
- Aching after sport rather than only during sport
- Limping after activity if symptoms are more irritable
- Tightness through the quadriceps, hip flexors, hamstrings or calves
- Pain that eases with rest but returns when training load increases again
- Symptoms in one knee or both knees
Aggravating Factors
- Jumping and landing, especially repeated jumps during basketball, netball, volleyball, gymnastics or athletics
- Running, sprinting and hill running
- Football codes involving kicking, acceleration, tackling and repeated direction changes
- Deep squats, lunges, step-downs or loaded leg exercises performed too early in rehab
- Kneeling directly on the painful lower kneecap
- Sudden increases in training frequency, intensity or competition load
- Playing multiple sports at the same time without enough recovery
- Training through pain during a growth spurt
- Hard playing surfaces or a rapid change in footwear
- Long sessions of stairs, hopping drills or plyometric training
Causes
Sinding-Larsen-Johansson syndrome develops when repeated pulling forces from the patellar tendon irritate its attachment at the lower part of the kneecap. In children and teenagers, this area is still developing and may be more sensitive to repeated loading, particularly during periods of rapid growth.
The patellar tendon is loaded every time a child jumps, lands, squats, sprints, kicks or changes direction. These activities are not harmful on their own. Symptoms are more likely to develop when the amount or intensity of activity exceeds what the developing knee can currently tolerate and recover from.
This is why SLJ syndrome is often considered a load tolerance problem. The knee is not necessarily seriously damaged; instead, the developing attachment at the bottom of the kneecap has become irritated from being repeatedly exposed to more load than it can comfortably manage.
Several factors can contribute to this mismatch between load and capacity:
- Growth spurts:
The developing attachment at the bottom of the kneecap can be particularly sensitive during periods of rapid growth. - Sudden increases in sport:
Pre-season training, tournaments, representative trials or returning to sport after a break can quickly increase the amount of stress placed through the knee. - Lots of running and jumping:
Sports such as basketball, netball, football, soccer, gymnastics and athletics repeatedly load the quadriceps and patellar tendon. - Playing multiple sports or teams:
Training and competing across several teams can make it difficult for the knee to get enough recovery between sessions. - Strength and movement capacity:
How a young athlete absorbs force when running, jumping, landing and changing direction can influence how much load is placed through the front of the knee.
The important point is that SLJ syndrome is usually not caused by one particular movement or injury. It more commonly develops when growth, sporting demands and recovery become temporarily out of balance.
How Is It Diagnosed?
Sinding-Larsen-Johansson syndrome is usually diagnosed clinically, meaning a physiotherapist can identify it through the history and physical examination without needing a scan in most cases. A physiotherapist will ask about:
- Where the pain is: pain is typically localised to the lower tip of the kneecap, where the patellar tendon attaches.
- What flares it: running, jumping, squatting, stairs, or kicking are common triggers.
- Training history: recent growth spurts, increases in training volume, new teams, carnivals, tournaments, or double-sport weeks.
- Symptom pattern: symptoms often build gradually and fluctuate with load, rather than appearing as a single traumatic injury.
Physical assessment often includes: palpation of the lower tip of the kneecap (usually tender), assessment of knee and hip strength, flexibility checks (especially quadriceps and hamstrings), and movement screening (squat, step-down, hopping, jumping or landing control) within comfort. In many cases, the diagnosis is straightforward when the pain is clearly at the lower tip of the kneecap and matches the activity triggers.
A key part of diagnosis is also ruling out other causes of anterior knee pain in adolescents, such as Osgood-Schlatter disease (pain further down at the bony bump at the top of the shin), patellar tendon pain, or less common conditions. If symptoms are unusual, severe, or not behaving as expected, your physiotherapist may refer to a GP for further assessment.
Investigations & Imaging
- X-ray
- May show fragmentation, irregularity or calcification at the lower pole of the patella. X-rays may be normal in early SLJ syndrome and are more useful when symptoms are persistent, severe, one-sided, traumatic, or when a fracture needs to be excluded.
- Ultrasound
- Can assess the patellar tendon attachment, local swelling, tendon thickening and changes at the inferior patellar pole. It can be useful when the clinical picture is unclear or when comparing the painful and non-painful side.
- Magnetic resonance imaging
- May show bone marrow swelling, inflammation at the patellar tendon attachment, tendon changes, or other causes of anterior knee pain. It is usually reserved for atypical symptoms, suspected sleeve fracture, significant swelling, locking, unexplained pain, or symptoms that are not improving as expected.
Physiotherapy Management
Exercise
Sinding-Larsen-Johansson physiotherapy exercises are used to reduce stress on the lower tip of the kneecap by improving strength and control across the whole lower limb, not just stretching the sore area. Your physiotherapist will tailor exercises to the child’s sport, pain level, growth stage and training week.
- Quadriceps strengthening:
The quadriceps connect into the patellar tendon, which attaches near the irritated lower tip of the kneecap in SLJ syndrome. Strengthening is important, but it needs to be introduced carefully. Early on, physiotherapists often use low-irritability exercises such as isometric knee extension holds, straight leg raises, controlled sit-to-stand patterns, or short-range knee extension. As symptoms settle, Sinding-Larsen-Johansson rehab may progress toward squats, step-ups, split squats and leg press within a pain-tolerable range. - Hip and glute strengthening:
Hip strength helps control the position of the thigh and knee during running, jumping and landing. If a child has poor hip control, more load may be placed through the front of the knee and the patellar tendon attachment. Exercises may include bridges, side-lying hip work, band walks, single-leg balance drills and gradual progression into sport-specific control exercises. - Calf and foot strength:
The calf muscles help absorb force when a child runs, jumps and changes direction. If the calf and foot are not contributing well, more stress may be passed up to the knee. Sinding-Larsen-Johansson physiotherapy exercises may include calf raises, skipping preparation, balance work and later-stage hopping drills when pain allows. - Landing and jumping mechanics:
SLJ syndrome often flares when a child returns too quickly to jumping, sprinting or sport-specific drills. A physiotherapist may retrain landing control using cues such as softer landings, bending through the hips and knees, and avoiding stiff or awkward landings. This becomes especially important before returning to training sessions, games and competitions. - Flexibility work:
Stretching may help if the quadriceps, hamstrings or calves are tight, especially during a growth spurt. However, stretching should be gentle and should not increase pain at the lower tip of the kneecap. Many children with SLJ syndrome need a combination of strength, load management and gradual return to sport rather than heavy stretching alone.
Activity Modification
Activity modification is one of the most important parts of physiotherapy for Sinding-Larsen-Johansson syndrome. The goal is not to stop all movement, but to reduce the specific loads that irritate the lower tip of the kneecap while keeping the child as active as possible.
- Reduce high-load activities temporarily:
A physiotherapist may recommend reducing jumping, sprinting, deep squatting, kicking volume, hill running, stairs and high-impact conditioning drills. These activities place higher load through the patellar tendon attachment at the lower kneecap and can keep SLJ syndrome irritated if they are continued at the same volume. - Use a traffic light system:
Green activities are comfortable and do not cause next-day pain. Amber activities cause mild symptoms but settle quickly. Red activities cause sharp pain, limping, swelling, or pain that lasts into the next day. This helps families and coaches make practical decisions about training and sport rather than guessing. - Modify sport instead of stopping everything:
Some children can keep participating with changes such as reduced training volume, skipping jumping drills, limiting game minutes, avoiding back-to-back matches, or removing painful conditioning work. Others may need a short break from sport if symptoms are more irritable. - Keep fitness with lower-impact options:
Swimming, cycling, upper-body gym work, walking within comfort, or modified skills training may help maintain fitness while the knee settles. Your physiotherapist can help choose options that do not repeatedly flare pain at the lower tip of the kneecap. - Build load back gradually:
Once symptoms are calmer, activity is usually reintroduced in stages. A physiotherapist may progress from basic strength exercises to running, jumping, landing drills and full sport. This helps the knee adapt to load again without repeatedly flaring Sinding-Larsen-Johansson syndrome.
Manual Therapy
Manual therapy does not directly “fix” the growth plate irritation in SLJ syndrome, but it can help reduce contributing stiffness and improve comfort. Physiotherapists may use soft tissue techniques for the quadriceps, hip flexors, hamstrings, calves or lateral thigh if these areas are increasing tension through the patellar tendon.
Gentle patellofemoral joint mobilisation, hip mobility work or ankle mobility treatment may be used if movement restrictions are changing how the child squats, lands or runs. Manual therapy should always support an active rehab plan. It is most useful when it helps the child move more comfortably and complete their Sinding-Larsen-Johansson physiotherapy exercises with better control.
Deep massage directly over the painful lower kneecap is usually avoided, especially when symptoms are irritable. The area is already sensitive to compression and pulling forces, so treatment should be comfortable and age-appropriate.
Postural Retraining
For SLJ syndrome, postural retraining is less about standing posture and more about how the leg handles load. A physiotherapist may assess single-leg squats, landing, running, cutting, jumping and stair control. Common findings include the knee dropping inward, poor hip control, stiff landings, overstriding, reduced ankle mobility or poor trunk control.
Movement retraining can reduce unnecessary stress through the patellar tendon attachment. This may include learning to land quietly, bend through the hips and knees, control knee alignment, spread load through the whole foot, and avoid repeated stiff-legged jumping. For kicking sports, a physiotherapist may also look at training volume, dominant leg load and repeated high-force kicking.
These changes are especially important before returning to sport. A child who only rests until pain improves may flare again when the same landing or running pattern is repeated at full speed. Good Sinding-Larsen-Johansson rehab prepares the knee for the actual movements the child needs in sport.
Bracing & Taping
A patellar tendon strap or taping may help some young people with SLJ syndrome by reducing discomfort during short periods of activity. It may slightly alter load through the patellar tendon and give the child confidence while symptoms are settling. Taping can also be useful during the transition back to training.
Bracing and taping should not be used to hide pain so a child can continue overloading the knee. If a strap allows a child to play but pain is worse afterwards or the next day, the total sport load is still too high. A physiotherapist can help decide whether taping or a strap is appropriate and how it fits into the broader physiotherapy plan.
Heat & Ice
Ice can be used after sport or after a flare-up if the lower kneecap feels sore, swollen or hot. It does not cure SLJ syndrome, but it may help with short-term pain relief. A typical approach is 10 to 15 minutes with a towel between the ice pack and skin.
Heat may be more useful for general muscle tightness around the thigh, especially before stretching or gentle exercise. Some children prefer heat and others prefer ice. Physiotherapy advice should focus on what helps symptoms without replacing the main treatment, which is load management and progressive strengthening.
Education
Education is a major part of physiotherapy for Sinding-Larsen-Johansson syndrome. Children, parents and coaches need to understand that SLJ syndrome is usually manageable, but it can persist if the knee is repeatedly overloaded during a growth spurt. Pain is a signal that the tendon attachment is irritated, not a sign that the child is weak or should avoid all activity forever.
A physiotherapist can explain how to adjust training, how to monitor symptoms, when to rest, when to progress, and how to return to sport safely. This may include planning recovery days, avoiding sudden spikes in training, limiting tournament load, modifying school sport, and using a gradual return-to-running or return-to-jumping plan.
Education also helps reduce anxiety. Many young athletes worry they will lose fitness or fall behind. A good physiotherapy plan keeps them involved where possible, builds strength during the recovery period and gives clear criteria for returning to sport.
Other
Balance and proprioception exercises may be included when the child has poor single-leg control or is returning to sports that require landing, pivoting and direction change. Examples include single-leg balance, reach tasks, controlled step-downs and landing drills.
Footwear and playing surface advice may be relevant if symptoms started after changing shoes, increasing court time, training barefoot, or moving to harder surfaces. Orthotics are not routinely required for SLJ syndrome, but a physiotherapist may consider foot mechanics if they are clearly contributing to poor lower-limb control or excessive knee load.
Other Treatments
Pain relief medication may be discussed with a pharmacist or doctor if pain is limiting sleep, school activity or basic walking. Medication may help symptoms in the short term, but it should not be used to allow a child to keep playing through worsening knee pain.
Relative rest is often helpful early on. This means reducing painful sport loads while keeping safe, comfortable activity in the week. Complete rest from all activity is not always necessary, but a short break from running and jumping may be useful when symptoms are irritable.
Coach-led training modification can be very helpful. For example, a young athlete may temporarily avoid jumping drills, reduce sprint volume, skip conditioning blocks, avoid deep squat strength work, or play fewer minutes. These decisions are best made with physiotherapy guidance so the child is not removed from sport for longer than needed.
Medical review is important if symptoms are severe, sudden, associated with a traumatic incident, or not improving with appropriate physiotherapy. Injections are not commonly used for SLJ syndrome in children and are generally not a routine treatment for this growth-related condition.
Surgery
Surgery is rarely needed for Sinding-Larsen-Johansson syndrome. Most young people improve with conservative treatment, especially when training load is managed properly and physiotherapy exercises are progressed gradually.
Surgical review may be considered if symptoms persist into adulthood, if there is a painful ossicle at the lower pole of the patella, or if another diagnosis is present. This is uncommon. Surgery is also relevant if the problem is not simple SLJ syndrome but a patellar sleeve fracture or another structural injury that requires orthopaedic management.
A physiotherapist plays an important role both before and after any surgical opinion. Before surgery is considered, physiotherapy can help confirm that a thorough conservative rehab plan has been completed. After surgery, physiotherapy is used to restore knee range of motion, rebuild quadriceps strength, retrain walking and gradually return the person to sport or activity.
Prognosis & Return to Activity
The outlook for Sinding-Larsen-Johansson syndrome is generally very good. Symptoms usually improve as the irritated area settles and the developing attachment at the bottom of the kneecap matures. How long this takes varies between children, and symptoms may come and go during periods of rapid growth or increased sporting activity.
Complete rest from sport is not usually necessary. Many children can continue participating with temporary changes to training, particularly by reducing activities that repeatedly flare their pain. As symptoms improve and the knee becomes more tolerant of load, running, jumping and sport can gradually be increased.
Return to full activity is usually guided by:
- Pain response: pain during activity remains mild and settles quickly, without a significant increase later that day or the following day.
- Everyday function: walking, stairs and squatting can be completed comfortably without limping or avoiding the affected leg.
- Sport tolerance: the child can progressively tolerate running, jumping, hopping and changing direction without a significant flare.
- Strength and control: strength and confidence have improved enough to manage the demands of their chosen sport.
Symptoms can fluctuate, particularly during growth spurts, tournaments or sudden increases in training. A flare does not necessarily mean the knee has been damaged again. It may simply mean the current sporting load is more than the knee can comfortably tolerate.
The goal of physiotherapy is therefore not to keep a child out of sport until they are completely pain-free. Instead, treatment aims to find the right balance between staying active, building the knee’s capacity and keeping symptoms manageable while the area continues to mature.
Complications
- Persistent anterior knee pain that limits sport, stairs, squatting or kneeling
- Recurrent flare-ups during growth spurts or sudden training increases
- Reduced quadriceps strength from avoiding knee loading for too long
- Altered running, landing or squatting mechanics due to pain
- Loss of fitness or confidence if the child fully stops activity without a structured rehab plan
- Confusion with other conditions such as patellar tendinopathy, Osgood-Schlatter disease or patellofemoral pain
- Rare persistence of symptoms into adulthood, sometimes associated with a painful ossicle
- Possible missed diagnosis of patellar sleeve fracture if pain begins suddenly after a forceful jump or injury
Preventing Recurrence
- Increase running, jumping and kicking loads gradually, especially during growth spurts when the lower kneecap is more sensitive to tendon traction.
- Avoid sudden spikes in sport, such as adding extra representative training, tournaments and school sport in the same week without recovery.
- Keep quadriceps, hip flexor, hamstring and calf flexibility within a comfortable range so the patellar tendon attachment is not exposed to unnecessary pulling stress.
- Build hip, quadriceps, hamstring and calf strength before increasing plyometrics, sprinting or high-volume court work.
- Use landing retraining to reduce stiff, noisy or knee-dominant landings that increase load through the patellar tendon.
- Monitor pain during and after sport. Pain that worsens during activity or lingers the next day usually means the knee has exceeded its current load tolerance.
- Plan recovery days between high-impact sessions rather than stacking multiple running and jumping sessions together.
- Modify training during periods of rapid growth rather than waiting until pain forces the child to stop completely.
- Avoid repeated kneeling on the painful lower patella during flare-ups, as direct compression can irritate symptoms.
- Maintain physiotherapy exercises after symptoms settle, particularly strength and landing-control work, to reduce the chance of recurrence.
When to See a Physio
- Knee pain is located at the bottom of the kneecap and keeps returning with sport.
- The child has pain with running, jumping, squatting, stairs or kneeling.
- Pain is causing limping after training or games.
- Symptoms are increasing during a growth spurt.
- The child has reduced sport participation because of anterior knee pain.
- Pain settles with rest but returns as soon as training resumes.
- There is uncertainty whether the problem is SLJ syndrome, Osgood-Schlatter disease, patellar tendinopathy or patellofemoral pain.
- The child needs a safe Sinding-Larsen-Johansson rehab plan for returning to football, netball, basketball, gymnastics, athletics, dance or other sport.
- Parents or coaches need guidance on how much sport is safe.
- Pain has not improved after a few weeks of sensible load reduction.