Morbus Sinding-Larsen-Johansson

Sinding-Larsen-Johansson disease (SLJ), also known as Sinding-Larsen disease or Larsen-Johansson syndrome, affects the proximal end of the patellar tendon as it inserts into the inferior pole of the patella. It represents a chronic traction injury of the immature osteotendinous junction. It is a closely related condition to Osgood-Schlatter disease. Some authors classify SLJ as a pediatric version of "jumper's knee" .

Epidemiology

Unlike "jumper's knee" which is seen at any age, Sinding-Larsen-Johansson disease is seen in active adolescents, typically between 10-14 years of age . Children with cerebral palsy are also prone to Sinding-Larsen-Johansson .

Clinical presentation

The presentation is with point tenderness at the inferior pole of the patella associated with focal swelling and restriction of knee joint range of movement .

Radiographic features

Plain radiograph

Early findings are subtle or absent. Thickening of the proximal patellar tendon may be seen with possible stranding of the adjacent portions of Hoffa's fat pad. Dystrophic calcification/ossification may eventually occur.

Ultrasound
  • thickening and heterogeneity of the proximal patellar tendon, especially involving the posterior fibers (which attach to the patella rather than pass over the surface of the patella to blend with the quadriceps tendon)
  • focal regions of hypoechogenicity may be seen, representing small tears.
MRI

MRI is useful in the assessment of extensor mechanism injuries.

  • the proximal and posterior part of the patellar tendon is thickened with high T2/STIR signal
  • often high T2/STIR signal in the inferior pole of the patella and in the adjacent fat

Treatment and prognosis

With rest and quadriceps flexibility exercises, the condition resolves with no secondary disability.

History and etymology

The entity was described by the Norwegian physician Christian Magnus Falsen Sinding-Larsen (1866-1930) in 1921 . The Swedish physician Sven Christian Johansson (1880-1959) described the same entity independently in 1922 .

Differential diagnosis

Imaging differential considerations include:

  • Osgood-Schlatter disease: occurs at the inferior attachment of the patellar tendon onto 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 sleeve fractures: same age group; avulsion of inferior pole cartilage, often with small fracture fragment
  • bipartite patella/normal inferior pole "fragmentation" 
  • infrapatellar bursitis: fluid signal is located anteriorly to the patellar tendon