A) Osgood-Schlatter’s disease
B) Iselin’s disease
C) Sever’s disease
D) Sinding-Larsen-Johansson disease
The extensor mechanism of the knee comprises the quadriceps tendon and muscles, patella, patellar ligament and the supporting retinaculum. Injuries can occur from direct trauma, overuse, degenerative disease. The most common adolescent injury to this area is Osgood-Schlatter’s disease (Fig. 1), which affects the distal pole of the patellar tendon and tibial tubercle.
Image 1: Common apophyseal injuries
At the inferior pole of the patella, Sinding-Larsen-Johansson syndrome and patellar sleeve avulsion fractures most commonly occur in adolescents with patellar tendinopathy occurring in both adults and adolescents. Patellar sleeve avulsion fractures occur usually with jumping and a full circumference of cartilaginous tissue and often a bony fragment is avulsed from the lower pole of the patella. SLJS is an osteochondrosis of the inferior pole of the patella and it frequently affects both knees. It is caused by traction on the patellar ligament, which causes inflammation at the insertion of the proximal tendon into the inferior pole of the patella. SLJS is commonly seen in active adolescents between 10 and 14 years of age . It can last on average around 9-10 months in the chronic phase.
The mechanism of injury is similar in all three of the entities and is believed to be due to forceful contraction of the quadriceps against resistance, particularly in adolescent male athletes. It can be difficult to differentiate between the diagnoses. SLJS can be distinguished from patellar tendinopathy by the presence of bone marrow edema over the patella. A patellar sleeve fracture is a traumatic separation of the distal articular cartilage with or without a bony fragment of the patellar body that is characterized by sudden pain and follows a single injury and normally affects one side .
Image 1. Arrow pointing to ossicle related to Sinding-Larsen-Johansson Syndrome on lateral radiograph. Adopted from .
Physical examination is important for the diagnosis of SLJS, as with most conditions. Most will have tenderness at the inferior pole of the patella and there may be some tenderness along the patellar tendon. Resisted knee extension may elicit pain and there may be some localized soft tissue swelling. A joint effusion should not be present with this condition and may be present with a patellar sleeve avulsion fracture.
Imaging will likely start with a plan radiograph with lateral radiographs being most useful. There may be peripatellar soft tissue swelling or patella alta. One or many osseous fragments may be present at the inferior pole of the patella. MRI (magnetic resonance imaging) can be helpful in showing whether or not edema or inflammation is present over the patella and will rule out any other internal derangement of the knee. On MRI, the inferior pole of the patella, proximal and posterior part of the patellar ligament and surrounding soft tissues are hypointense on T1-weighted MRI sequences and hyperintense on T2-weighted MRI (fat-suppression) sequences (Image 2). Ultrasound images were shown as either equally effective as, or more effective than radiographs, especially when evaluating the soft tissue. Ultrasound is proposed as a simple and reliable method for diagnosing knee-joint osteochondrosis, especially during the early stages of the disease (Image 3). Ultrasound is also suitable for periodic follow-up in the course of the disease . On ultrasound, the lower pole of the patella appears fragmented and hypoechoic with swelling of the cartilage, in particular at the insertion of the patellar ligament. Follow-up examinations demonstrate progressive consolidation of the affected bone.
Image 2: MRI T2 image showing bony edema over inferior pole of the patella. Adopted from .
Medlar and Lyne documented the self-limiting natural history in ten knees . They classified the condition in four stages based on the radiographs. The following stages were proposed: stage I when the patella has a normal appearance, stage II if there are irregular calcifications in the distal pole, stage III with coalescence of calcifications, stage IV-a when the calcifications are coalescing into the distal pole, and stage IV-b is a calcified ossicle distinct from the distal pole.
Initial treatment consists of relieving the pain by resting for a few days and strengthening exercises with modification of activities. There is no definite protocol or treatment algorithm that exists for SLJS. Non-steroidal anti-inflammatory drugs (NSAIDs) may be necessary, and in severe cases a cast is used for maintaining immobility. This is usually done for up to 4 weeks, but most cases do not require this. Many can perform weight bearing as tolerated and physical therapy may be prescribed. Two separate reports have shown an average return to sport in 4-14 weeks with the average age of 8 to 14 years old with almost all cases happening in athletes, with soccer and males being more common [5-7]. Treatment is typically guided by pain and activities. Crutches may be needed if limping is occurring and an experienced physical therapist or athletic trainer can aid in progression and return to activity or sport. Surgical debridement, which will remove the necrotic intratendinous tissue should be the last resort for patients who are resistant to conservative management.
Image 3. Ultrasound images of SLJS showing hyperemia (neovascularity) noted with Doppler over inferior patellar pole with normal opposite knee in the right image. Adopted from .
In summary, Sinding-Larsen-Johansson syndrome (SLJS) is caused by traction on the patellar ligament, causing inflammation at the insertion of the proximal ligament into the inferior pole of the patella. It is technically an osteochondrosis and should be differentiated from a patellar sleeve fracture and patellar tendinopathy. Treatment is largely nonsurgical and conservative measure with relative rest and possibly immobilization and therapy are common treatments.
Answer D. The clinical vignette describes the apophyseal injury known as Sinding-Larsen-Johansson disease or syndrome, which is caused by traction on the patellar ligament, causing inflammation at the insertion of the proximal ligament into the inferior pole of the patella. This is distinct from Osgood Schlatter’s disease, which is a similar traction apophysitis that occurs at the distal patellar tendon and tibial tubercle. Iselin’s disease is an apophysitis that occurs at the base of the fifth metatarsal and Sever’s disease occurs at the distal Achilles insertion and calcaneus.
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