Sinding Larsen Johansson Syndrome: Symptoms, Types, Causes and Treatment

Sinding-Larsen-Johansson syndrome (SLJ) is a lesser-known but significant cause of knee pain in growing children and adolescents, particularly those who are physically active. Sometimes confused with other knee disorders, SLJ can impact daily activities and athletic participation. Understanding its symptoms, variations, underlying causes, and the latest treatment approaches is crucial for timely recognition and effective management. This article provides a comprehensive, evidence-based overview of Sinding-Larsen-Johansson syndrome, drawing on the latest clinical research and real-world cases.

Symptoms of Sinding Larsen Johansson Syndrome

Recognizing the symptoms of SLJ is the first step toward early diagnosis and successful treatment. SLJ typically presents in active children and teenagers, affecting knee function and, in some cases, causing significant discomfort.

Main Symptom	Additional Features	Patient Group	Source(s)
Anterior knee pain	Swelling at lower patella	Active adolescents	1, 2, 3, 4, 6, 7
Pain on flexion	Functional limitation	Athletes	1, 3
Tenderness	Radiographic abnormalities	Juvenile athletes	7
Bilateral cases	Often during activity	10–14 years old	3, 4

Table 1: Key Symptoms

Common Clinical Presentation

SLJ syndrome most often manifests as pain at the front of the knee, specifically near the lower (inferior) pole of the patella. This pain is usually aggravated by activities that load the knee, such as running, jumping, or kneeling. Swelling may also be observed below the kneecap. Adolescents involved in high-level sports are particularly susceptible, and the condition can sometimes affect both knees simultaneously 1, 2, 3, 4.

Activity-Related Discomfort

One striking feature of SLJ is the connection between symptoms and physical activity. Pain typically worsens during or after sports, especially those with repetitive jumping or squatting. Functional limitations, such as difficulty climbing stairs or squatting, are common 1, 3.

Physical and Imaging Findings

On examination, doctors often find tenderness and sometimes visible swelling at the inferior pole of the patella. Imaging—like ultrasound, X-ray, or MRI—may reveal characteristic changes such as calcification or irregularities at the attachment site of the patellar tendon 1, 4, 7.

Symptom Duration and Progression

The duration of symptoms can vary widely, lasting from a few weeks to several months. In most cases, symptoms are self-limited and resolve with appropriate management 1, 2, 6. However, in rare cases, persistent pain may interfere with sports or daily life, necessitating more aggressive intervention 8.

Types of Sinding Larsen Johansson Syndrome

SLJ syndrome isn't a single uniform entity—variations exist depending on severity, radiographic appearance, and associated injuries. Recognizing these types is vital for tailoring treatment and prognosis.

Type/Variant	Distinguishing Feature	Typical Patient	Source(s)
Classic SLJ	Osteochondrosis at patella	Active children	3, 4, 6
Bilateral SLJ	Both knees affected	Adolescents	2, 4
SLJ with calcification	Visible on radiographs	Juvenile athletes	7
SLJ with avulsion fracture	Overlap with sleeve avulsion	Rare/acute cases	4, 9

Table 2: Types and Variants

Classic Sinding-Larsen-Johansson

The hallmark presentation is osteochondrosis—disruption of normal development—at the lower pole of the patella. This form is most frequent in active children and early adolescents (ages 10–14) 3, 6.

Bilateral and Atypical Cases

While most cases present in one knee, bilateral involvement can occur, particularly in highly active individuals 2, 4. These cases may complicate diagnosis and management, as symptoms can be more pronounced or persistent.

Radiographic Stages and Calcification

Radiographic findings vary and can include irregular or regular calcifications at the inferior patella, coalescence (merging) of the calcification, or even separation from the patella 7. These features may not always match the clinical stage, making diagnosis sometimes challenging.

SLJ Overlapping with Avulsion Fracture

Rarely, SLJ can overlap or be confused with acute injuries such as patellar sleeve avulsion fractures—where a fragment of cartilage and bone is pulled off by the tendon 4, 9. These cases may require different management, including possible surgery, highlighting the need for precise diagnosis.

Causes of Sinding Larsen Johansson Syndrome

Understanding what leads to SLJ is essential for prevention, early detection, and management. Though the exact cause isn't always clear, several risk factors and mechanisms have been identified.

Main Cause	Associated Risk Factors	Biomechanical Links	Source(s)
Repetitive microtrauma	High-level sports, jumping	Short hamstrings, tibial slope	2, 3, 6, 8
Traction tendinitis	Patellar tendon stress	Patella alta (rare)	6, 7
Biomechanical variance	Increased posterior tibial slope	Knee alignment issues	2
Growth-related changes	Skeletal immaturity	Rapid growth phases	2, 6

Table 3: Causes and Risk Factors

Repetitive Microtrauma

SLJ is most often caused by repetitive stress on the patellar tendon where it attaches to the lower pole of the patella. This typically occurs in children and adolescents participating in jumping or running sports, leading to overuse injury and inflammation 1, 3, 6, 8.

Traction Tendinitis and Calcification

The condition is considered a form of traction tendinitis—chronic pulling at the tendon attachment, sometimes resulting in micro-avulsion (tiny tears) and calcification at the site 6. Over time, this can cause pain, swelling, and radiographic changes.

Biomechanical and Anatomical Factors

Recent studies have identified biomechanical contributors. Children with SLJ often have:

• Shortened hamstring tendons, limiting flexibility
• Increased posterior tibial slope, altering knee mechanics

These factors may place additional stress on the patellar tendon during activity, increasing SLJ risk 2. Although patella alta (a high-riding patella) and other alignment issues have been studied, their role is less clear 2, 7.

Growth Spurts and Skeletal Maturity

SLJ almost exclusively affects skeletally immature individuals—those whose bones are still growing. Rapid growth may exacerbate tendon-bone stress as the muscles and bones mature at different rates 2, 6.

Treatment of Sinding Larsen Johansson Syndrome

The vast majority of SLJ cases are self-limited and respond well to conservative management. However, recognizing when more intensive treatment is needed is key to restoring function and preventing complications.

Treatment Approach	Key Measures	Indications/Outcome	Source(s)
Activity modification	Rest, avoid aggravating sports	Most cases, full recovery	1, 2, 3, 4, 6
Physical therapy	Stretching, strengthening	Persistent symptoms	8
Imaging-guided diagnosis	Ultrasound, X-ray, MRI	Accurate diagnosis	1, 4, 7, 9
Surgical intervention	Arthroscopic excision, fixation	Rare, refractory cases	8, 9

Table 4: Treatment Strategies

Conservative Management

Most cases of SLJ syndrome resolve with non-surgical management:

• Rest and Activity Modification: Limiting or stopping sports and activities that stress the knee is the primary recommendation. This gives the tendon-bone interface time to heal 1, 2, 3, 4.
• Physical Therapy: Targeted exercises, including hamstring and quadriceps stretching and strengthening, help restore flexibility and function, and address biomechanical factors 8.
• Analgesia and Support: Ice, anti-inflammatory medications, and knee supports may be used to manage pain during recovery.

Imaging and Monitoring

Proper imaging—ultrasound, X-ray, or MRI—is crucial for diagnosis, monitoring progress, and ruling out related conditions like patellar sleeve avulsion 1, 4, 7, 9.

Surgical Options

Rarely, when conservative treatment fails or if there is an associated fracture (such as a sleeve avulsion), surgical intervention may be necessary:

• Arthroscopic Excision: Removal of symptomatic lesions has been successful in adults with persistent SLJ 8.
• Fixation for Avulsion Fractures: When bone is displaced, surgical repair (using suture tapes or other fixation) is required to restore knee function 9.

Prognosis

With appropriate treatment, the prognosis is excellent. Most children return to their previous activity levels within a few months, with complete resolution of symptoms 1, 2, 6, 8. Surgical outcomes are generally favorable if required, but most cases do not need it.

Conclusion

Sinding-Larsen-Johansson syndrome is an important, though often under-recognized, cause of knee pain in young athletes. Its hallmark is activity-related pain at the lower patella, with both clinical and imaging findings guiding diagnosis. While most cases resolve with conservative management, awareness of its types, causes, and rare complications is essential for optimal care.

Key Takeaways:

• SLJ primarily affects active, growing adolescents—especially boys engaged in sports.
• Symptoms include activity-related anterior knee pain, swelling, and tenderness at the patellar tendon insertion.
• Variations include bilateral cases and overlap with acute injuries like patellar sleeve avulsion.
• Causes center on repetitive microtrauma and biomechanical factors such as tight hamstrings and increased tibial slope.
• Conservative treatment with rest and physical therapy is highly effective; surgery is rarely needed.
• Early diagnosis and appropriate management ensure full recovery and return to activity.

Understanding SLJ enables clinicians, parents, and young athletes to recognize symptoms early, seek timely medical attention, and prevent long-term complications.