Bilateral deep infrapatellar bursitis associated with tibial tuberosity enthesopathy in a case of juvenile ankylosing spondylitis

A Case of Chronic Deep Infrapatellar Bursitis Complicated by Patellar Tendinopathy and its Evaluation With Musculoskeletal Ultrasound

Knee pain is a very common complaint in routine physiatry and orthopedic practice. While bursitis is a well-known and common cause of knee pain, deep infrapatellar bursa (DIPB) involvement is relatively less common. Inflammation of DIPB occurs commonly due to either direct trauma or overuse, but other rare causes have also been reported in the literature including infection, juvenile idiopathic arthritis, gout, and juvenile ankylosing spondylitis. We report a case of chronic inflammation of DIPB caused by direct trauma and associated with patellar tendinopathy. Additionally, we describe the characteristic findings on musculoskeletal ultrasonography (MSK-USG). For ultrasound evaluation, the patient should lie supine with the knee slightly flexed. Deep infrapatellar bursitis can be seen as an anechoic fluid-filled structure immediately posterior to the distal patellar tendon and anterior to the tibial tuberosity. While MRI can confirm the diagnosis of bursitis, MSK-USG can be quick, highly sensitive, and is able to confirm the diagnosis as well as to detect dynamic changes in the patellar tendon and adjacent structures. USG can also help in the treatment by guiding corticosteroid injection into the bursa. Activity modification and eccentric exercises play an important role in the rehabilitation program in these cases.

MR imaging of extrasynovial inflammation and impingement about the knee

The knee has unique anatomy regarding the relationship between the synovial and capsular layers, with interposed fat pads at certain locations. The extrasynovial impingement and inflammation syndromes about the knee are underdiagnosed and should be included in the differential diagnosis of anterior knee pain. MR imaging is the best imaging modality for evaluation of the anatomy and disorders of these extrasynovial compartments.

Entheses and enthesitis: a histopathologic review and relevance to spondyloarthritides

There are two types of entheses: fibrous, by Sharpey's fibers in membranous bone, and fibrocartilaginous, on endochondral bone, with discontinuous cement lines at the interface between insertion and bone. The connection of hyaline cartilage to subchondral bone is a kind of fibrocartilaginous enthesis. Fibrocartilages are structurally, chemically, and biomechanically intermediate between tendon and cartilage. Enthesitis is not the sole pathologic feature of spondyloarthritides. Synovitis and subchondral bone marrow changes outside the ligamentous insertions, and cartilage proliferation, are important too. In the subentheseal bone marrow and in the synovium, CD8+ T cells play a central role. Imaging of early changes is better achieved by ultrasonography and even better by magnetic resonance imaging than by radiography. No single immunologic target can be identified. The G1 domain of aggrecan is the best candidate, but this does not apply to fibrous entheses. In these complex pathologic conditions, no single abnormality can thus far be designated as a unique hallmark.

Enthesiopathy: clinical manifestations, imaging and treatment

Enthesitis is a distinctive pathological feature of spondyloarthropathy and may involve synovial joints, cartilaginous joints, syndesmoses and extra-articular entheses. This review focuses on peripheral extra-articular enthesitis which is a clinical hallmark of spondyloarthropathy. The entheses of the lower limbs are more frequently involved than those of the upper limbs, and heel enthesitis is the most frequent. Entheseal pain may be mild or moderate as well as severe and disabling. Peripheral enthesitis may be observed in all forms of spondyloarthropathy, including the undifferentiated ones, and may for a long time be the only long-standing clinical manifestation of the B27-associated disease process. Various imaging methods have been suggested for studying peripheral enthesitis. Ultrasonography and magnetic resonance imaging are the most useful because they may show alterations of the structures involved. Therapy of peripheral enthesitis consists of NSAIDs, orthoses and physical therapy. Steroid injections, second line drugs such as sulphasalazine and radiotherapy are reserved for more severe cases.

The anatomy of the deep infrapatellar bursa of the knee

Disorders of the deep infrapatellar bursa are important to include in the differential diagnosis of anterior knee pain. Knowledge regarding its anatomic location can aid the clinician in establishing a proper diagnosis. Fifty cadaveric knees were dissected, and the deep infrapatellar bursa had a consistent anatomic location in all specimens. The deep infrapatellar bursa was located directly posterior to the distal 38% of the patellar tendon, just proximal to its insertion on the tibial tubercle. There was no communication to the knee joint. Its average width at the most proximal margin of the tibial tubercle was slightly wider than the average distal width of the patellar tendon. It was found to be partially compartmentalized, with a fat pad apron extending down from the retropatellar fat pad to partially divide it into anterior and posterior compartments. The recommended approach to this bursa, either for aspiration, injection, or surgery, is along the lateral edge of the patellar tendon just proximal to the tibial tubercle.

Septic bursitis

Nine cases of septic bursitis are presented, and the literature on the subject comprehensively reviewed, with an emphasis on the clinical manifestations of septic bursitis in various anatomic locations. Physical activities associated with increased susceptibility to septic bursitis and systemic conditions that increase the severity of septic bursitis are catalogued. Analysis of the microbiology of cases reported in the literature demonstrates that greater than 80% of cases of septic bursitis are caused by Staphylococcus aureus and other gram-positive organisms. However, a wide variety of gram-negative microorganisms, fungi, and other infectious agents have been reported to cause septic bursitis and may lead to complications in diagnosis and treatment. The nine cases reported here demonstrate the potential severity of septic bursitis and emphasize that significant systemic complications may result from this common musculoskeletal infection. Indications for hospitalization and/or intravenous antibiotic therapy for septic bursitis include the presence of fulminant local infection, evidence for systemic toxicity, or infection in an immunocompromised patient. Patients who fail to respond to intravenous antibiotics and percutaneous aspiration of the bursa may require surgical drainage or bursectomy by one of several methods that have been proposed. There is some recent evidence that intrabursal corticosteroid injection for therapy of nonseptic subcutaneous bursitis may be more effective than systemic antiinflammatory medication or simple bursa aspiration.

Conservative Treatment of Inflamed Knee Bursae

In brief Knee bursitis often mimics other brief Pathologies, making correct diagnosis necessary to initiate appropriate treatment. Most commonly affected are the prepatellar, pes anserine, tibial collateral ligament, and two infrapatellar bursae. Other common bursitic conditions include Baker's cysts and posttraumatic adventitious hemorrhagic bursitis. Most of these can be treated conservatively with aspiration of fluid from the bursa, rest, ice, immobilization, and injection of a corticosteroid and analgesic combination. Some chronic bursitic conditions may require surgical excision of the bursa.