Sinding Larsen Johansson syndrome (SLJS) is a juvenile osteochondrosis and traction epiphysitis affecting the extensor mechanisms of the knee, disrupting the attachment of the patella tendon to the inferior pole of the patella. Patellar inferior pole tenderness often accompanied by X-rays showed evidence that the pole was split. Most patients with SLJS also have calcifications in the inferior pole of the patella. 
The syndrome usually appears during the growth spurt of puberty. It is associated with localized pain that is exacerbated by movement. Local tenderness and soft tissue swelling are usually observed. There is also tightness in the quadriceps, hamstrings and surrounding muscles Especially the gastrocnemius. This tightness often results in inflexibility of the knee, which alters the stress through the patellofemoral joint. 
Image 1: Site of Osgood Schlatter’s disease and SJS of the knee. OSG at the tibial trochanter and SJS at the inferior pole of the patella
Medlar and Lyne classified the condition into four stages based on radiographs. The following stages are proposed: Stage I, when the patella is normal in appearance; Stage II, if there are irregular calcifications at the distal pole; Stage III, if the calcifications are confluent; Stage IV-a, when Calcification fused to the distal pole, stage IV-b is calcified ossicles distinct from the distal pole .
Unlike jumper’s knee, which can be seen at any age, SLJS is common in active adolescents, usually between the ages of 10-14.
- Children with cerebral palsy are also susceptible to SLJS .
SLJS is caused by patellar tendon stretching, causing inflammation where the proximal ligament inserts into the inferior pole of the patella.
The extensor mechanism of the knee consists of the quadriceps tendon and muscles, the patella-patella ligament and the bracing retinaculum. Direct trauma, overuse and degenerative diseases can cause injury. The most common juvenile injury in this region is Osgood-Schlatter disease Affects the distal end of the patellar tendon and tibial tuberosity. 
As in most cases, a physical examination is important for the diagnosis of SLJS. Most will have extreme tenderness under the patella, and there may be some tenderness along the patellar tendon. Resisting knee extension may cause pain, and there may be some localized soft tissue swelling. Instead of joint effusion, a patellar cuff avulsion fracture may occur. 
Patients are usually active boys between the ages of 10 and 13. Symptoms are usually;
- Even worse is the exercise climbing stairs squatting knee jumping and running.
- May report that they limp after exercise.
- May be unilateral or bilateral.
- Is relieved by rest
Sinding-Larsen-Johansson syndrome is a self-limited syndrome. Closure of the patellar growth plate is expected to allow full recovery. Although symptoms of Sinding-Larsen-Johansson syndrome may persist for months, few patients do not respond well to conservative and surgical management Generally no intervention is required. Corticosteroid injections are not recommended due to case reports of subcutaneous atrophy. 
Differential considerations include:
- Osgood-Schlatter disease: occurs when the patellar tendon attaches to the tibial tuberosity
- Jumper’s knee: same location and similar pathology, but seen in adults (some authors do not distinguish between Sinding-Larsen-Johansson and jumper’s knee).
- Patellar cuff fracture: same age group; inferior pole cartilage avulsion often accompanied by small fracture fragments
- Bipartite Patella/Normal Lower Pole Fracture
- Subpatellar bursitis: fluid signal located in front of the patellar tendon 
A physical therapist performs a physical examination of the knee and checks the patient’s symptoms. If you have pain in the front of your knee, there are three important tests to do. During all tests, the patient was in the supine position.
- Patella grinding test ; the tester places the thumb mesh space above the patella and is then asked to forcefully contract the quadriceps. If there is pain or friction, the test is positive.
- Compression testing ; downward force applied to rotate pain indicates meniscal injury.
- Extension Resistance Test
The Kujala Anterior Knee Pain Scale and Lower Extremity Function Scale can be used both as an initial screening tool and to detect post-treatment changes and outcome measures.
Initial treatment includes resting for a few days to relieve pain and intensifying exercise with changes in activities. There are no clear protocols or treatment algorithms for SLJS. Nonsteroidal anti-inflammatory drugs (NSAIDs) may be necessary in severe cases Plaster is used to keep it still. This usually lasts up to 4 weeks, but most cases do not need to be done. Many can do weight bearing as tolerated, and physical therapy is available.
- Two separate reports showed an average return to sport within 4-14 weeks, with a mean age of 8 to 14 years, with almost all cases occurring in soccer players and more commonly in male athletes.
- Treatment is usually guided by pain and activity. If a limp develops, crutches may be needed, and an experienced physical therapist or athletic trainer can help with progression and return to activity or sport.
- Surgical debridement will remove necrotic endotendinous tissue and should be a last resort in patients resistant to conservative treatment. 
Physical Therapy Treatment
Physiotherapists must educate patients on mobility modifications.
Kneeling, jumping, squatting, climbing stairs and running with the affected knee should be avoided, at least in the short term.
Lower body strength needs to be tested, especially in the ankles and hips, to detect any muscle weakness that may lead to overuse syndrome.
Core strengthening and exercises that address flexibility or strength issues should be started.  Treatment should include eccentric exercise and isokinetic strengthening. 
Example of a standing calf stretch.
If the patient is unresponsive (no pain relief), platelet-rich plasma injections may be given. These are performed in the cartilage synchronization zone under ultrasound guidance.  Stretching and proprioceptive muscle strengthening exercises for patients with anterior knee pain has been shown to be beneficial.  Improvements in strength and function can be achieved with open and closed kinetic chain exercises.  Patients who underwent a 30- to 60-minute physical therapy intervention once a week for six weeks demonstrated a reduction in patellofemoral pain. 
It may be safe to return to sports or high-level activity when each of the following occurs in this specific order:
- The lower kneecap is no longer tender and swollen.
- The injured knee can be fully straightened and bent without pain.
- The knee and leg have regained normal strength compared to the uninjured knee and leg
- Ability to jog straight ahead without limp.
- Ability to sprint forward in a straight line without limp.
- Ability to do 45-degree cuts.
- Ability to do 90-degree cuts.
- Capable of running a 20-yard figure eight.
- Capable of running a 10-yard figure eight.
- Ability to hop with both legs without pain and with the injured leg without pain. 
If it does not progress, surgery may be required. During the first week after surgery, full weight bearing with two canes can be performed without an immobilizing splint. Knee exercises can then be started a week later to restore joint range of motion. The first six weeks will Including eccentric quadriceps exercises and jumping, other more functional movements were allowed after three months. This strategy is again only used in one specific patient and has not been fully studied. 
- Medlar, R. C., et al., ‘Sinding-Larsen-Johansson Disease. Its Etiology and Natural History’, Journal of Bone & Joint Surgery, December 1978, vol. 60, no. 8, p. 1113-1116. (Level of Evidence 1B)
- Houghton, K. M., ‘Review for the generalist: evaluation of anterior knee pain’, Paediatric Rheumatology, (2007), vol. 5, p. 4-10. (Level of Evidence 2B)
- The sports medicine review SINDING-LARSEN-JOHANSSON SYNDROME Available: https://www.sportsmedreview.com/blog/sinding-larsen-johansson-syndrome/ (accessed 13.10.20210
- Radiopedia Sinding-Larsen-Johansson disease Available: https://radiopaedia.org/articles/sinding-larsen-johansson-disease (accessed 13.10.2021)
- http://slideplayer.com/slide/4311148/, Hip, Thigh, and Knee. ILIUM Acetabulum Ischium Ischial Tuberosity Pubis. (Photo)
- http://www.slideshare.net/JLS10/kin191-ach6kneepatellofemoralevaluation (Photo)
- http://www.fpnotebook.com/ortho/exam/AplysCmprsnTst.htm (Photo)
- https://meded.ucsd.edu/clinicalmed/neuro2.htm (Photo)
- Klucinec, B., ‘Recalcitrant Infrapatellar Tendinitis and Surgical Outcome in a Collegiate Basketball Player: A Case Report’, Journal of Athletic Training, June 2001, vol. 36, no. 2, p. 174-181. (Level of Evidence 1C)
- Demetrious, T. and B., Harrop (red.), Sinding-Larsen-Johansson Disease, internet, 2008, (http://www.physioadvisor.com.au/10246650/sindinglarsenjohansson-disease-physioadvisor.htm). (Level of Evidence 5)
- Clark, D.I., et al., ‘Physiotherapy for Anterior Knee Pain. A Randomised Controlled Trial’, Ann Rheum Dis, 2000, 59, p. 700-704. (Level of Evidence 1B)
- Witvrouw, E., et al., ‘Open Versus Closed Kinetic Chain Exercises for Patellofemoral Pain. A Prospective Randomised Study’, The American Journal of Sports Medicine, 2000, vol. 28, no. 5, p. 687-694. (Level of Evidence 1B)
- Crossley, K., et al., ‘Physical Therapy for Patellofemoral Pain. A Randomised, Double-Blinded, Placebo-Controlled Trial’, The American Journal of Sports Medicine, 2002, vol. 30, no. 6, p. 856-865. (Level of Evidence 1B)