Patellar Apophysitis is irritation and inflammation of the growth plate (apophysis) at the bottom of the patella (kneecap), where the patella tendon inserts. In a child, the bones grow from areas called growth plates. Apophysitis and osteochondrosis are common causes of pain in growing bones but have differing etiologies and required management. Apophysitis results from a traction injury to the cartilage and bony attachment of tendons in children and adolescents. Most often it is an overuse injury in children who are growing and have tight or inflexible muscle-tendon units. Apophysitis occurs in upper and lower extremities, it occurs more often in the lower extremities, with common locations including the patellar tendon attachment at the patella or tibia (i.e., Larsen-Johansson and Osgood-Schlatter diseases), the calcaneus (i.e., Sever disease), and multiple locations around the body.
Other Names
- Traction apophysitis of the knee
- Sinding-Larsen-Johansson Disease
- Sinding Larsen Johansson Disease (SLJ)
- Superior Patellar Pole Apophysitis
- Inferior Patellar Pole Apophysitis
Pathophysiology
Anatomic illustration of Sinding Larsen Johansson Syndrome.jpg
- General
- Overuse injury at the inferior pole of the patella at the proximal patella tendon attachment
- Repetitive traction on the patellar ligament due to quadriceps contraction causes inflammation of patellar tendon attachment
- Leads to cartilage damage, swelling, and pain
- Later tendon thickening and fragmentation of the lower pole of the patella
- Present in skeletally immature adolescents (age 10-14)
- Considered stress fractures of the apophyseal physis
- Analogous to a nondisplaced Salter-Harris 1 fracture
Causes
-
- Regular physical activity
- Excessive physical activity is most common (i.e. overuse)
- Direct trauma to the inferior pole of the patella
Associated Pathology
- Osgood Schlatter Disease
- Infrapatellar Bursitis
Pathoanatomy
- Patella
- The largest sesamoid bone of the skeleton
- The patellar tendon arises from the inferior patella and inserts distally into the tibial tuberosity
- Extensor mechanism: Quadriceps attaches to Patella, Patella Tendon inserts on Tibial Tubercle
- Ossification begins at 3-5 years
- Apophysis at the inferior pole of the patella
- Opens at age 10, closes at age 14
Risk Factors
- General
- Middle school athletes
- Practice > competition
- Involvement in competitive sport at the age (around 5 or 6 years old) in which the patella begins its ossification
- Sport specialization
- Sports (high demands on the extensor apparatus)
- Football
- Running
- Volleyball
- Gymnastics
- Long Jump
- Karate
- Biomechanical/ Structural
- Short hamstring tendon
- Increased posterior tibial slope
Differential Diagnosis
- Fractures
- Distal Femur Fracture
- Patellar Fracture
- Tibial Plateau Fracture
- Dislocations & Subluxations
- Patellar Dislocation (and subluxation)
- Knee Dislocation
- Proximal Tibiofibular Joint Dislocation
- Muscle and Tendon Injuries
- Quadriceps Contusion
- Iliotibial Band Syndrome
- Quadriceps Tendonitis
- Patellar Tendonitis
- Popliteus Tendinopathy
- Extensor Mechanism Injury
- Patellar Tendon Rupture
- Quadriceps Tendon Rupture
- Patellar Fracture
- Ligament Pathology
- ACL Injury
- PCL Injury
- MCL Injury
- LCL Injury
- Meniscal Pathology
- Posterolateral Corner Injury
- Multiligament Injury
- Arthropathies
- Knee Osteoarthritis
- Septic Arthritis
- Gout
- Bursopathies
- Prepatellar Bursitis
- Pes Anserine Bursitis
- MCL Bursitis
- Infrapatellar Bursitis
- Patellofemoral Pain Syndrome (PFPS)/ Anterior Knee Pain)
- Chondromalacia Patellae
- Patellofemoral Osteoarthritis
- Osteochondral Defect Knee
- Plica Syndrome
- Infrapatellar Fat Pad Impingement
- Patellar Instability
- Neuropathies
- Saphenous Nerve Entrapment
- Other
- Bakers Cyst
- Patellar Contusion
- Pediatric Considerations
- Patellar Apophysitis (Sinding-Larsen-Johansson Disease)
- Patellar Pole Avulsion Fracture
- Tibial Tubercle Avulsion Fracture
- Tibial Tuberosity Apophysitis (Osgood Schalatters Disease)
Diagnosis
- History
- History of insidious onset of pain on the anterior aspect of the knee
- Duration is weeks to months
- Worse when the patella is loaded (running, jumping, sudden stops)[6]
- Physical Exam: Physical Exam Knee
- Tenderness over the inferior patella may extend into the tendon
- Swelling over the inferior patella, Knee Effusion should be absent
- Range of motion normal or slightly limited in flexion due to pain
- Strength and extension should be intact but painful
- Special Tests
- Jump Test: Pain is easily reproduced with repetitive jumping in the examination room
Lateral left knee radiograph with an arrow demonstrating loose bony fragments at the inferior patellar pole[7]
Radiographs
- Standard Radiographs Knee
- Findings
- It May be normal or show spur at the inferior pole of the patella
- Soft tissue swelling may be noted on the lateral view
- Can see calcifications at the origin of the patellar tendon
Focal thickening increased echogenicity of the right infrapatellar tendon (compared to left). Arrow indicates significant widening, cortical irregularity associated with the apophysis of the patellar apex.
Ultrasound
- General
- The imaging modality of choice as it can identify all pathology associated with the disease
- May follow serially over time to examine for progression/resolution of disease
- Findings[9]
- Cartilage swelling or thickening
- Tendon thickening
- Fragmentation of the lower pole
- Infrapatallar bursitis
- Hyperemic tendon fibers with power doppler
MRI
-
- If diagnosis unclear
- Help distinguish from patellar sleeve avulsion
Classification
Unknown Classification System
- Stage 1: Pain occurs after activity
- Stage 2: Pain present while performing the activity and persists after activity
- Stage 3: Pain affecting/limiting function during activity
Iwamoto Classification System
- Based on radiographic findings[10]
- Stage 1: Normal findings.
- Stage 2: Irregular calcifications at the inferior patellar pole.
- Stage 3: Coalescence of calcifications.
- Stage 4A: Incorporation of calcifications into the patella.
- Stage 4B: Coalesced calcified mass separate from the patella
Treatment
Nonoperative
- The mainstay of treatment, usually self-limited
- Activity modification
- Abstain for 1-2 months minimum
- Consider replacing with swimming, other sports that don’t use quadriceps muscle as much
- NSAIDS
- Physical therapy
- Improve hamstring, quadriceps, and heel cord flexibility
- Patellar Tendon Counterforce Strap
- May provide relief, can be worn as needed
- Consider biomechanical evaluation if not improving
- Look for knee twisting, valgus moment
- Neuromuscular deficits
- Contraindicated
- Corticosteroid Injection
Operative
- Indications
- Refractory to nonoperative treatment
- Technique
- Debridement of damaged tissue/stimulation of healing response
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