Suprapatellar bursitis is a common cause of anterior knee pain. The suprapatellar bursa lies between the anterior surface of the distal femur and the distal quadriceps musculotendinous unit (Fig. 143.1). The bursa serves to cushion and facilitate sliding of the musculotendinous unit of the quadriceps muscle over the distal femur. The bursa is subject to inflammation from a variety of causes with acute trauma to the knee and repetitive microtrauma being the most common. Acute injuries to the bursa can occur from direct blunt trauma to the anterior knee from falls onto the knee as well as from overuse injuries including running on uneven or soft surfaces or jobs that require crawling on the knees like carpet laying. If the inflammation of the bursa is not treated and the condition becomes chronic, calcification of the bursa with further functional disability may occur. Gout and other crystal arthropathies may also precipitate acute suprapatellar bursitis as may bacterial, tubercular, or fungal infections.

The patient suffering from suprapatellar bursitis most frequently presents with the complaint of pain in the anterior knee, which may radiate superiorly into the distal thigh. The patient may find walking down stairs and kneeling increasingly difficult. Physical examination of the patient suffering from suprapatellar bursitis will reveal point tenderness over the superior-anterior knee. If there is significant inflammation, rubor and color may be present and the entire area may feel boggy or edematous to palpation. Active resisted extension and passive flexion of the affected knee will often reproduce the patient’s pain. Sudden release of resistance to active extension will markedly increase the pain. If calcification or gouty tophi of the bursa and surrounding tendons are present, the examiner may appreciate crepitus with active extension of the knee, and the patient may complain of a catching sensation when moving the affected knee, especially on awaking. Often, the patient will not be able to sleep on the affected side. Occasionally, the suprapatellar bursa may become infected, with systemic symptoms, including fever and malaise, as well as local symptoms, with rubor, color, and dolor being present.

Plain radiographs are indicated in all patients who present with knee pain to rule out occult bony pathology (Fig. 143.2). Based on the patient’s clinical presentation, additional testing may be indicated, including complete blood cell count, sedimentation rate, and antinuclear antibody testing. Magnetic resonance imaging or ultrasound imaging of the affected area may also confirm the diagnosis and help delineate the presence of other knee bursitis, calcific tendonitis, tendinopathy, quadriceps tendonitis, or other knee pathology (Figs. 143.3 and 143.4). Rarely, the inflamed bursa may become infected, and failure to diagnose and treat the acute infection can lead to dire consequences.

There is significant intrapatient variability in the size of the suprapatellar bursa. The suprapatellar bursa lies between the anterior surface of the distal femur and the distal quadriceps musculotendinous unit (see Fig. 143.1). The bursa serves to cushion and facilitate sliding of the musculotendinous unit of the quadriceps muscle over the distal femur (Fig. 143.5). The suprapatellar bursa is held in place by a small portion of the vastus intermedius muscle, called the articularis genus muscle. Both the quadriceps tendon and the suprapatellar bursa are subject to the development of inflammation caused by overuse, misuse, or direct trauma. The quadriceps tendon is made up of fibers from the four muscles that comprise the quadriceps muscle: the vastus lateralis, the vastus intermedius, the vastus medialis, and the rectus femoris. These muscles are the primary extensors of the lower extremity at the knee. The tendons of these muscles converge and unite to form a single, exceedingly strong tendon. The patella functions as a sesamoid bone within the quadriceps tendon, with fibers of the tendon expanding around the patella and forming the medial and lateral patella retinacula, which help strengthen the knee joint. These fibers are called expansions and are subject to strain; the tendon proper is subject to the development of tendonitis. The suprapatellar, infrapatellar, and prepatellar bursae also may concurrently become inflamed with dysfunction of the quadriceps and patellar tendon.