74 Bursitis

Bursitis

Sam Y. Chun, Ali Islam, Alison Spouge, Anthony G. Ryan, and Peter L. Munk

Clinical Presentation

A 45-year-old woman with a 1-week history of increasing anterior knee pain and swelling presented to us. Physical exam showed focal soft-tissue swelling and erythema over the front of the knee.

Figure 74A

Figure 74B (see also Figure 74B in color insert.

A long axis sonogram at the anterior aspect of the knee (Fig. 74A) shows a large, irregular fluid-and debris-containing collection (white arrows) with thick, irregular walls. The deep surface of the collection contacts the anterior aspect of the patella and patellar tendon (black arrows).

A long axis sonogram (Fig. 74B in the same location as (Fig. 74A with color Doppler shows prominent hyperemia (white arrow).

Diagnosis

Septic prepatellar bursitis.

Differential Diagnosis

Infected versus noninfected bursitis
Cellulitis
Hematoma/seroma
Abscess

Discussion

Background

Bursae are sacs lined by endothelial cells that serve to reduce friction at sites where tendons, muscle, and bone glide over each other. Constant bursae are formed during normal development, and adventitious bursae are formed when there is abnormal friction and stress, causing myxomatous degeneration of fibrous tissue at pressure points. Deep bursae frequently communicate with the adjacent joint.

Risk factors for bursitis include occupations requiring repetitive motion, increased age, gout, rheumatoid arthritis, and concurrent bacterial infection. In athletes, the incidence of bursitis has been reported to be as high as 10%, and in the general population, it accounts for < 0.5% of visits to primary-care facilities.

Common sites for bursitis include the shoulder (subacromial/subdeltoid bursa, subscapular bursa), olecranon bursa, iliopsoas bursa, ischiogluteal bursa, greater trochanter bursa, prepatellar bursa, deep and superficial infrapatellar bursae, Baker’s cyst, and retrocalcaneal and pre-Achilles’ bursae. Adventitious bursae are found in sites where there are pseudoarthroses, exostoses, or malalignment of a joint, such as hallux valgus.