SINDING-LARSEN-JOHANSSON SYNDROME
Inferior Pole Patellar Apophysitis | Adolescent Athletes | Activity Modification | Self-Limiting
SEVERITY GRADING
Critical Must-Knows
- Traction apophysitis: Repetitive stress on inferior pole of patella from patellar tendon during growth spurt
- Self-limiting condition: Resolves when apophysis closes (typically 1-2 years), may leave painless calcification
- Clinical diagnosis: Point tenderness over inferior pole of patella, worsened by resisted knee extension
- Treatment is conservative: Activity modification, ice, stretching - rarely any surgery needed
- Less common than OSD: Similar mechanism but affects proximal end of patellar tendon
Examiner's Pearls
- "Less common than Osgood-Schlatter but same mechanism and treatment
- "Bilateral in 20-30% but usually asymmetric
- "Often coexists with Osgood-Schlatter disease
- "Persistent calcification at inferior pole after resolution is normal
Clinical Imaging
Imaging Gallery
Critical Sinding-Larsen-Johansson Exam Points
Mechanism and Timing
Traction apophysitis at inferior pole of patella. Repetitive contraction of quadriceps pulls on inferior pole via patellar tendon origin. Peak age 10-14 years (slightly younger than OSD). More common in jumping/running sports (basketball, soccer, gymnastics, volleyball).
Clinical Features
Point tenderness over inferior pole of patella is pathognomonic. Pain worsened by running, jumping, kneeling, squatting, stairs. Reproduced by resisted knee extension and passive flexion. May have palpable calcification. No effusion, no instability.
Imaging Role
X-rays NOT required for diagnosis - clinical diagnosis. If obtained, may show soft tissue swelling, fragmentation, or irregular ossification at inferior pole. Reserve X-rays for: atypical presentation, ruling out tumor/infection, failed treatment, suspected avulsion fracture.
When to Refer
Most cases managed in primary care. Refer if: symptoms persist beyond skeletal maturity, complete avulsion fracture suspected, concern for other diagnoses (tumor, infection), severe symptoms not responding to conservative care after 6 months.
Quick Decision Guide - Anterior Knee Pain in Adolescents
| Condition | Key Features | Tenderness Location | Management |
|---|---|---|---|
| Sinding-Larsen-Johansson | 10-14y athletes, activity-related pain | Inferior pole of patella | Activity modification, stretching, ice |
| Osgood-Schlatter | 10-15y athletes, activity-related pain, bump | Tibial tubercle (anterior, distal to patella) | Same conservative treatment as SLJ |
| Patellofemoral pain syndrome | Anterior knee pain, worse sitting/stairs | Diffuse peripatellar, retropatellar | VMO strengthening, patellar taping |
| Patellar tendinopathy (jumper's knee) | Older athletes (16+), jumping sports | Inferior pole patella to tendon insertion | Eccentric exercises, load management |
| Inferior pole avulsion fracture | Acute traumatic event, swelling, unable to extend | Inferior pole with deformity | URGENT - surgical fixation usually needed |
SLJSLJ - Clinical Features
Memory Hook:SLJ affects the Superior-Lower Junction of the patellar tendon - where it originates from the inferior pole of the patella.
INFERIORINFERIOR - Location and Features
Memory Hook:INFERIOR pole is where the patellar tendon originates - this is the proximal end of the extensor mechanism, opposite to OSD at the distal end.
TREATTREAT - Treatment Approach
Memory Hook:TREAT SLJ with Tender care - this is self-limiting, don't over-treat.
Overview and Epidemiology
Sinding-Larsen-Johansson (SLJ) Syndrome is a traction apophysitis affecting the inferior pole of the patella in active adolescents. It is characterized by localized pain, swelling, and tenderness at the origin of the patellar tendon on the inferior pole of the patella.
Epidemiology:
- Less common than Osgood-Schlatter disease but same mechanism
- Peak incidence: males 11-14 years, females 10-13 years
- Male to female ratio approximately 2:1
- 20-30% bilateral (often asymmetric in severity)
- Most common in running, jumping, kicking sports (soccer, basketball, gymnastics, volleyball)
- Often coexists with Osgood-Schlatter disease (both ends of patellar tendon affected)
Why During Growth Spurt?
The inferior pole of the patella has a secondary ossification center (apophysis) that is biomechanically weaker than mature bone or the patellar tendon. During the adolescent growth spurt, rapid bone growth increases muscle-tendon tension while the apophysis has not yet fused. Repetitive traction from the powerful quadriceps causes microtrauma, inflammation, and sometimes fragmentation of the apophysis at the patellar tendon origin.
Etiology and Risk Factors:
Intrinsic Factors
- Age: Skeletal immaturity with open patellar apophysis
- Sex: Male more common (puberty timing, sports participation)
- Rapid growth: Growth spurt increases tension
- Quadriceps tightness: Tight quads increase traction force
- Hamstring tightness: Adds load to extensor mechanism
Extrinsic Factors
- High-impact sports: Running, jumping, kicking
- Training volume: Intense practice schedules during growth
- Poor conditioning: Sudden increase in activity level
- Hard playing surfaces: Increase impact loading
- Inadequate rest periods: No recovery time between training
Natural History:
- Most cases resolve spontaneously when the patellar apophysis fuses (typically 1-2 years)
- Residual calcification at inferior pole may persist - this is NORMAL, not a complication
- 5-10% have persistent symptoms into adulthood
- Rare complications: inferior pole avulsion fracture, persistent symptomatic calcification
Pathophysiology and Mechanisms
Inferior Pole Patella Anatomy
The inferior pole of the patella is where the patellar tendon originates. The patella has a secondary ossification center at its inferior pole that appears during childhood and fuses during adolescence.
Patellar Apophysis Development
| Stage | Age (years) | Description | Clinical Relevance |
|---|---|---|---|
| Cartilaginous | 0-8 | Entirely cartilage, no ossification | Rarely symptomatic at this age |
| Apophyseal | 8-12 | Secondary ossification center appears at inferior pole | Beginning of vulnerability period |
| Epiphyseal | 10-14 | Ossification extends, peak vulnerability | Peak SLJ incidence |
| Fusion | 14-18 | Apophysis fuses to patella | SLJ symptoms resolve with fusion |
Inferior Pole Avulsion
The cartilaginous apophysis is the weak link. During the epiphyseal stage, the inferior pole may avulse with acute trauma (jumping sports, landing). Unlike SLJ, avulsion is an ACUTE injury with sudden pain, inability to extend knee, and visible/palpable deformity. Treat as a fracture - usually requires surgical fixation.
Extensor Mechanism Biomechanics
Quadriceps Force Transmission
Quadriceps muscle generates force that is transmitted through:
- Quadriceps tendon → inserts on superior pole of patella
- Patella → acts as sesamoid/pulley
- Patellar tendon → originates from inferior pole, inserts on tibial tubercle
In growing adolescents, the inferior pole apophysis experiences HIGH tensile stress at the tendon-bone junction.
Why Inferior Pole?
- Tendon origin: Patellar tendon originates from inferior pole
- Peak stress at origin: Tendon-bone junction concentrates force
- Weak link: Cartilaginous apophysis weaker than tendon or bone
- Growth-related tension: Rapid femoral growth increases quad tightness
Relationship to Osgood-Schlatter
SLJ and OSD affect opposite ends of the patellar tendon. SLJ affects the origin (inferior pole of patella) while OSD affects the insertion (tibial tubercle). Both are traction apophysitides with the same mechanism, age group, and treatment. Patients may have both conditions simultaneously, representing stress at both ends of the extensor mechanism.
Classification Systems
Clinical Severity Grading
| Grade | Symptoms | Impact on Activity | Treatment Approach |
|---|---|---|---|
| Mild | Pain only after activity, no swelling at rest | Can complete training sessions | Ice after activity, stretching, continue sports |
| Moderate | Pain during AND after activity, mild swelling | Performance affected, some activity limitation | Modify activity level, patellar strap, formal physio |
| Severe | Pain at rest, limits daily activities, walking painful | Unable to participate in sport | Rest from sport, possible short immobilization, physio |
Severity Guides Duration
Mild SLJ may improve in 6-8 weeks with basic activity modification. Moderate SLJ typically requires 3-6 months of modified activity. Severe SLJ may need 6-12 months, possibly with periods of complete rest. All grades typically resolve when the physis closes, but symptom duration is proportional to severity.
Clinical Assessment
History:
Key Questions
- Age and sex: Peak 10-14 years, more common in males
- Sports participation: Type, frequency, intensity
- Training changes: Recent increase in volume or intensity?
- Pain characteristics: Location, timing, aggravating factors
- Bilateral symptoms: 20-30% bilateral
- Previous injury: Rule out acute trauma
- Coexisting OSD: Check for tibial tubercle symptoms
Red Flags
- Night pain or rest pain: Consider tumor, infection
- Acute traumatic onset: Avulsion fracture
- Knee effusion: Unusual for SLJ - suggests other pathology
- Systemic symptoms: Fever, weight loss - infection, malignancy
- Very young child: Under age 8 - SLJ rare, investigate
- Hip symptoms: SCFE, Perthes - examine hip in all knee pain
Physical Examination:
Systematic Examination
- Visible swelling over inferior pole of patella (less common than OSD bump)
- Compare bilateral - may be asymmetric if bilateral SLJ
- Look for effusion (unusual for SLJ - suggests other diagnosis)
- Assess overall limb alignment, muscle bulk
- Point tenderness over inferior pole of patella - pathognomonic
- Palpate entire patellar tendon (rule out tendinopathy)
- Palpate tibial tubercle (check for coexisting OSD)
- Palpate medial and lateral joint lines (meniscal pathology)
- Palpate patella and peripatellar tissues
- Knee ROM: Usually full, may have slight flexion discomfort
- Passive flexion: May be painful at end range (compresses inferior pole)
- Quadriceps and hamstring flexibility: Often reduced
- Hip ROM: Must examine hip to rule out referred pain (SCFE)
- Resisted knee extension: Reproduces pain over inferior pole
- Active knee extension: May be painful against resistance
- Patellar mobility: Normal in SLJ (unlike patellofemoral syndrome)
- Ligament stability: Should be normal
- Meniscal tests: Should be negative
Always Examine the Hip
SCFE and Perthes disease commonly present as knee pain in children due to referred pain along the obturator nerve. In ANY child presenting with knee pain, especially if obesity or limited hip ROM is present, you MUST examine the hip. Missing SCFE can lead to avascular necrosis and hip destruction.
Investigations
Clinical Diagnosis
Sinding-Larsen-Johansson is a CLINICAL diagnosis. Imaging is NOT required in typical cases. Key clinical features (point tenderness over inferior pole of patella in athletic adolescent during growth spurt) are sufficient for diagnosis. Reserve imaging for atypical presentations or to exclude other pathology.
When to Order Imaging:
Indications for X-ray
- Acute traumatic event (rule out avulsion fracture)
- Atypical age (too young or too old for SLJ)
- Night pain or rest pain (rule out tumor)
- Effusion (unusual for SLJ)
- Failure to improve with 3-6 months conservative treatment
- Suspected loose ossicle in symptomatic adult
What X-rays Show
- Soft tissue swelling anterior to inferior pole
- Fragmentation of inferior pole ossification center
- Irregular ossification of apophysis
- Separate ossicle at inferior pole (may persist)
- Calcification at inferior pole post-fusion
Other Imaging:
| Modality | Indication | Findings | Clinical Use |
|---|---|---|---|
| Lateral X-ray | First-line if imaging needed | Soft tissue swelling, fragmentation, ossicle | Confirm diagnosis, rule out fracture |
| Ultrasound | Assess patellar tendon, soft tissues | Tendon thickening, fragmentation, bursa | Useful if tendinopathy suspected |
| MRI | Rule out tumor, stress fracture, infection | Edema at inferior pole, soft tissue changes | Rarely needed - reserve for red flags |
Management Algorithm
Non-Operative Management (First-Line for ALL Cases)
95%+ of SLJ resolves with conservative treatment alone.
Conservative Treatment Protocol
- Do NOT stop all activity - reduce intensity and volume
- Avoid painful activities (deep squats, jumping, kneeling)
- Continue sport at reduced level if tolerable
- Cross-train with low-impact activities (swimming, cycling)
- Ice after activity (15-20 minutes) for symptom relief
- Quadriceps stretching: Reduces traction force on inferior pole
- Hamstring stretching: Decreases quadriceps demand
- Hip flexor stretching: Improves mechanics
- Hold stretches 30 seconds, 3-4 times daily
- Dynamic warm-up before activity
- Eccentric quadriceps: Once acute pain settles
- Core stability: Reduce load on knee during activity
- Hip strengthening: Improve biomechanics
- Progress gradually as symptoms allow
- Patellar strap/brace: Reduces traction on inferior pole
- Knee pad: Protects inferior pole when kneeling
- NSAIDs: Short-term for acute flares (not long-term)
- Ice/heat: Symptom relief
Avoid Complete Rest
Prolonged complete rest is NOT recommended. It weakens muscles, detrains the athlete, and delays return to sport. Modify activity to a tolerable level rather than stopping entirely. The exception is severe cases with rest pain, which may need a short period of immobilization.
Surgical Technique
Ossicle Excision (Adults Only)
Surgery Rarely Needed
Surgery for Sinding-Larsen-Johansson syndrome is extremely rare and reserved for symptomatic ossicle in adults (post-skeletal maturity) or persistent pain from calcification. Surgery is NOT indicated for active SLJ in adolescents.
Indications:
- Skeletal maturity (closed patellar apophysis)
- Persistent focal pain over ossicle
- Failed conservative management (6+ months)
- Imaging confirms symptomatic ossicle at inferior pole
Technique:
- Longitudinal or transverse incision over inferior pole
- Identify ossicle at patellar tendon origin
- Excise ossicle, debride tendon edges
- Repair tendon if needed
- Some surgeons also smooth prominent inferior pole
This is a straightforward procedure with excellent outcomes in appropriately selected patients.
Complications
Complications and Long-Term Sequelae of SLJ
| Complication | Incidence | Risk Factors | Management |
|---|---|---|---|
| Persistent calcification | Common (30-50%) | Part of natural history | Reassurance - cosmetic only, does not affect function |
| Inferior pole avulsion fracture | Rare (less than 1%) | Acute trauma in severe SLJ | Surgical ORIF if displaced, cast if non-displaced |
| Symptomatic ossicle in adult | 5-10% | Large initial ossicle, non-compliance | Ossicle excision if failed conservative treatment |
| Patellar tendinopathy | Uncommon | Return to sport too early, ongoing overuse | Eccentric loading program, activity modification |
| Pain with kneeling | 10-20% | Calcification persists | Knee pads, reassurance, rarely surgical reduction |
Avulsion Fracture Not Same as SLJ
Inferior pole avulsion fracture is DIFFERENT from SLJ. Avulsion is acute, traumatic, with sudden pain and inability to extend knee. It requires urgent orthopaedic referral. SLJ is chronic, overuse, with gradual onset and preserved extension. Do not confuse these conditions.
Postoperative Care and Rehabilitation
Rehabilitation for Ossicle Excision (Adults)
Post-Ossicle Excision Protocol
- Weight-bearing as tolerated
- ROM exercises as comfort allows
- Ice, elevation for swelling
- Gentle quadriceps sets
- Full ROM expected by 6 weeks
- Progressive strengthening
- Bike, swimming for cardio
- Avoid deep squats, jumping
- Sport-specific training
- Plyometrics progression
- Jogging, running progression
- Full return based on strength testing
- Typically 3-4 months for full competition
- Ongoing maintenance stretching
Rehabilitation for Conservative SLJ (Adolescents)
This is the main patient population - structured rehab program while continuing modified activity:
- Daily stretching: Quadriceps, hamstrings, hip flexors (30 sec × 3)
- Eccentric strengthening: When acute pain settles
- Core stability exercises
- Sport modification: Continue at reduced level
- Ice after activity
- Gradual progression as symptoms allow
Outcomes
Long-Term Outcomes:
- Excellent prognosis - most cases resolve completely with skeletal maturity
- Symptoms typically improve within 1-2 years (when patellar apophysis fuses)
- Persistent calcification at inferior pole is common but NOT a functional problem
- Most athletes return to full sport without long-term issues
- 5-10% have some adult symptoms, usually mild or related to ossicle
Predictors of Prolonged Course:
- Severe initial presentation
- Delay in activity modification
- Ongoing intense sports participation without modification
- Bilateral involvement
- Coexisting Osgood-Schlatter disease
The Calcification is Normal
Parents often worry about the residual calcification at the inferior pole. Reassure them this is part of the normal healing process - the calcification represents bone that formed during the inflammatory phase and is now incorporated into the mature patella. It is cosmetic only and does not affect function or sports performance.
Evidence Base
Natural History of Sinding-Larsen-Johansson Syndrome
- Retrospective review of 42 patients with SLJ
- All patients had resolution of symptoms with skeletal maturity
- Residual calcification at inferior pole common but asymptomatic
- No long-term functional limitations
Conservative Management Outcomes
- Comprehensive review of apophysitis management
- Activity modification and stretching are mainstays of treatment
- Complete rest not recommended - modify activity level
- Surgery rarely indicated in adolescents
Patellar Strap Effectiveness in Apophysitis
- RCT comparing patellar strap vs no strap in apophysitis
- Patellar strap group had faster symptom resolution
- Significant improvement in pain scores with strap use
- Strap may reduce traction force on apophysis
Ossicle Excision in Adults
- Retrospective study of ossicle excision in military personnel
- 89% good/excellent results at mean 10-year follow-up
- Mean return to duty 3.4 months postoperatively
- Low complication rate
Risk Factors for Apophysitis
- Prospective cohort study of 1854 adolescents
- High sports participation volume associated with apophysitis
- Quadriceps tightness was a significant risk factor
- Rapid growth was associated with increased incidence
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Scenario 1: Initial Presentation (~2-3 min)
"A 12-year-old boy who plays basketball presents with 2 months of anterior knee pain. The pain is worse after training and he has point tenderness at the front of his knee."
Scenario 2: Coexisting Conditions (~3-4 min)
"A 13-year-old female gymnast presents with bilateral anterior knee pain. On examination, she has tenderness at both the inferior pole of the patella and the tibial tubercle bilaterally."
Scenario 3: Avulsion Fracture (~2-3 min)
"A 14-year-old basketball player jumps for a rebound and lands with sudden severe knee pain. He cannot extend his knee and you notice tenderness and swelling over the inferior pole of the patella."
MCQ Practice Points
Distinguishing SLJ from Avulsion
Q: An adolescent presents with knee pain after jumping. How do you distinguish SLJ from avulsion fracture? A: SLJ has GRADUAL onset, pain during/after activity, ability to extend knee, and no visible deformity. Avulsion has ACUTE onset after trauma, inability to extend knee, visible/palpable deformity, and severe pain. X-ray shows displaced fragment in avulsion vs fragmentation in SLJ.
When to Image
Q: Which of the following is an indication for X-ray in suspected SLJ? A: Night pain (rule out tumor), acute traumatic onset (rule out avulsion), failure to improve after 6 months conservative treatment, atypical age (less than 8 or after skeletal maturity). Routine SLJ does NOT require imaging.
Treatment Approach
Q: What is the recommended activity level for adolescent with SLJ? A: Activity MODIFICATION, not complete rest. Continue sport at reduced level if tolerable. Avoid painful activities (deep squats, kneeling, jumping). Cross-train with low-impact activities. Complete rest weakens muscles and delays return.
Natural History
Q: What happens to the calcification after SLJ resolves? A: The inferior pole calcification typically persists as a painless, cosmetic finding in 30-50% of patients. This represents ossification that occurred during the healing process and is now incorporated into the mature patella. It is NOT a complication and does not affect function.
Differential Diagnosis
Q: A 12-year-old with knee pain has point tenderness at the INFERIOR POLE of patella. What is the diagnosis? A: Sinding-Larsen-Johansson syndrome - traction apophysitis at the inferior pole of patella (where patellar tendon originates). Same mechanism as Osgood-Schlatter but at the proximal end of the patellar tendon. Treatment is identical - activity modification, stretching, ice.
Relationship to OSD
Q: How does SLJ differ from Osgood-Schlatter disease? A: SLJ affects the inferior pole of the patella (patellar tendon origin) while OSD affects the tibial tubercle (patellar tendon insertion). Both are traction apophysitides with the same mechanism, age group, and treatment. Patients may have both conditions simultaneously.
Australian Context and Medicolegal Considerations
Epidemiology in Australia
- Common in Australian adolescents, particularly in popular sports (AFL, soccer, basketball, netball)
- Equal or increasing incidence in females with increased sports participation
- Managed primarily in general practice and sports medicine clinics
Access to Care
- Most cases managed in primary care without specialist referral
- Physiotherapy widely available through Medicare (5 sessions under Chronic Disease Management plan) or private
- Sports medicine physicians manage more complex cases
- Orthopaedic referral rare - mainly for suspected avulsion or refractory adult symptoms
Medicolegal Considerations:
Key Documentation Requirements
Key documentation points:
- Clear history of gradual onset and activity-related symptoms
- Documentation of point tenderness specifically over inferior pole of patella
- Hip examination performed (to exclude SCFE/Perthes)
- Discussion of self-limiting nature and expected timeline
- Activity modification advice given (not complete rest)
Don't Miss SCFE: SCFE commonly presents as knee pain in obese adolescent males. Missing SCFE diagnosis causes significant morbidity from AVN. Document hip examination in ALL adolescents presenting with knee pain. This is a frequent source of litigation in pediatric orthopaedics.
Prevention Strategies:
- Sports Medicine Australia guidelines emphasize load management
- School and club sports programs increasingly aware of growth spurt risks
- Pre-season screening programs may identify at-risk athletes
SINDING-LARSEN-JOHANSSON SYNDROME
High-Yield Exam Summary
Key Anatomy
- •Inferior pole of patella = patellar tendon origin
- •Secondary ossification center at inferior pole
- •Apophysis fuses during adolescence (14-18 years)
- •Opposite end of patellar tendon from Osgood-Schlatter
Diagnosis
- •Clinical diagnosis - imaging not required
- •Point tenderness over inferior pole of patella
- •Pain with resisted knee extension
- •10-14 years, athletic, growth spurt
Treatment
- •Activity MODIFICATION not complete rest
- •Stretching: quads, hamstrings, hip flexors
- •Ice after activity (15-20 min)
- •Patellar strap during sport
- •NSAIDs short-term for flares only
Imaging Indications
- •Acute traumatic onset (avulsion)
- •Night pain (tumor)
- •Failure after 6 months conservative
- •Atypical age or presentation
Red Flags
- •Acute trauma with inability to extend = AVULSION
- •Night/rest pain = tumor, infection
- •Knee effusion = not typical for SLJ
- •Hip symptoms = SCFE, Perthes
Prognosis
- •90%+ resolve with skeletal maturity
- •Duration 1-2 years (until physis closes)
- •Calcification persists but is painless
- •5-10% adult symptoms (usually ossicle)