Osgood-Schlatter disease

Osgood-Schlatter disease (OSD) is a chronic fatigue injury due to repeated microtrauma at the patellar ligament insertion onto the tibial tuberosity, usually affecting boys between 10-15 years.

Epidemiology

Osgood-Schlatter disease is seen in active adolescents, especially those who jump and kick, and because of this, is seen more frequently in boys. It is bilateral in up to 25-50% of patients ^1-3. Typical age of onset in females may be slightly earlier (boys 10-15 years; girls 8-12 years) ⁸.

Clinical presentation

Clinically, patients present with pain and swelling over the tibial tuberosity, exacerbated with exercise.

Radiographic features

Plain radiograph

Soft tissue swelling with loss of the sharp margins of the patellar tendon are the earliest signs in the acute phase; thus a compatible history is also essential in making the diagnosis. Bone fragmentation at the tibial tubercle may be evident 3 to 4 weeks after the onset.

It is important not to equate isolated 'fragmentation' of the apophysis with OSD, as there may well be secondary centres of ossification.

Ultrasound

Ultrasound examination of the patellar tendon can depict the same anatomic abnormalities as can plain radiographs, CT scans, and magnetic resonance images. The sonographic appearances of Osgood-Schlatter disease include ³:

• swelling of the unossified cartilage and overlying soft tissues
• fragmentation and irregularity of the ossification centre with reduced internal echogenicity 
• thickening of the distal patellar tendon
• infrapatellar bursitis

MRI

MRI, as expected, is more sensitive and specific, and will demonstrate:

• soft-tissue swelling anterior to the tibial tuberosity
• loss of the sharp inferior angle of the infrapatellar fat pad (Hoffa's fat pad)
• thickening and oedema of the inferior patellar tendon
• infrapatellar bursitis (clergyman's knee)
  • a distended deep infrapatellar bursa can be a frequent finding ⁶
• bone marrow oedema may be seen at the tibial tubercle 

Treatment and prognosis

Treatment is usually conservative and involves rest, ice, activity modification - decreasing activities that stress the insertion (especially jumping or lunging sports), quadriceps and hamstring strengthening exercises. Analgesia and padding to prevent pressure on the tibial tubercle are also useful. Only rarely are therapeutic casts required ^4-5. 

The condition spontaneously resolves once the physis closes.

In rare cases, surgical excision of the ossicle and/or free cartilaginous material may give good results in skeletally mature patients, who remain symptomatic despite conservative measures. 

Unresolved OSD is the term given to clinical and radiological findings of OSD that persist into adulthood.

History and etymology

It is named after:

• Robert B. Osgood: Boston orthopaedic surgeon (1873-1956)
• Carl Schlatter: Swiss professor of surgery (1864-1934)

Differential diagnosis

Imaging differential considerations include:

• Sinding-Larsen-Johansson syndrome: equivalent condition involving the inferior pole of the patella
• jumper's knee: involves the patellar tendon rather than the bone, and is essentially a tendinopathy with focal tenderness, although it may eventually be associated with bony changes (some authors do not distinguish between SLJ and jumper's knee) 
• infrapatellar bursitis