Deep infrapatellar bursitis

Deep infrapatellar bursitis refers to an inflammation of the deep infrapatellar bursa and is an uncommon condition in children.

Epidemiology

Risk factors

Sports and activities involving a great amount of running and jumping are considered risk factors for developing deep infrapatellar bursitis ¹.

Associations

Deep infrapatellar bursitis is associated with the following conditions ¹:

• juvenile idiopathic arthritis
• synovitis of the knee
• Osgood-Schlatter disease
• ankylosing spondylitis

Clinical presentation

Patients may complain about localized anterior swelling more prominent on extension possibly associated with anterior knee pain in particular with extreme flexion and/or extension, but the presentation can be variable. Inflammatory markers might be elevated ¹.

Pathology

Like other types of bursitis deep infrapatellar bursitis is characterized by inflammation of the bursal synovium and is associated with the formation of an increased amount of fluid and collagen.

Etiology

Deep infrapatellar bursitis may have the following causes ^1,2:

• excessive friction due to repetitive stress or overuse activity
• acute trauma

Radiographic features

Findings of deep infrapatellar bursitis will be most evident on ultrasound and MRI and are then seen as fluid accumulation within the distended bursa.

Plain radiograph

Lateral view of the knee might show obliteration of the posterior border of the distal patella tendon and loss of the fat plane at the location of the deep infrapatellar bursa.

Ultrasound

Ultrasound might show the following in the infrapatellar region:

• distended deep infrapatellar bursa/cystic mass
• internal septations
• heterogeneous soft tissue mass

MRI

Typically MRI will show the following ^1,2:

• distension of the deep infrapatellar bursa
• thickening of the bursal synovium best appreciated after contrast administration
• possible concomitant synovitis of the knee joint

Signal characteristics

• T2: hyperintense
• T1: hypointense
• T1 C+ (Gd): contrast enhancement of the synovial lining

Radiology report

The radiological report should include a description of the following:

• signs of bursitis that is distension of the bursa and possible rim enhancement
• alterations of the patellar tendon if present
• associated findings e.g. knee joint effusion or synovitis

Treatment and prognosis

Deep infrapatellar bursitis can be managed conservatively. Treatment includes temporary activity modification, physical therapy, nonsteroidal anti-inflammatory drugs and direct injections of lidocaine and/or corticosteroids ¹.

Differential diagnosis

Conditions that can mimic the presentation and/or the appearance of deep infrapatellar bursitis include:

• Osgood-Schlatter disease
• jumper's knee
• superficial infrapatellar bursitis

See also

• cyst-like lesions around the knee