THE CLINICAL SYNDROME
The suprapatellar bursa is vulnerable to injury from both acute trauma and repeated microtrauma. The suprapatellar bursa extends superiorly from beneath the patella under the quadriceps femoris muscle. This bursa may exist as a single bursal sac or, in some patients, as a multisegmented series of sacs that may be loculated in nature. Acute injuries frequently take the form of direct trauma to the bursa via falls directly onto the knee or from patellar fractures, as well as from overuse injuries, including running on soft or uneven surfaces, or from jobs that require crawling on the knees, such as carpet laying. If the inflammation of the suprapatellar bursa becomes chronic, calcification of the bursa may occur.
The patient suffering from suprapatellar bursitis will frequently complain of pain in the anterior knee above the patella that can radiate superiorly into the distal anterior thigh. Often, the patient will be unable to kneel or walk down stairs. The patient may also complain of a sharp, catching sensation with range of motion of the knee, especially on first arising. Suprapatellar bursitis often coexists with arthritis and tendinitis of the knee joint, and these other pathological processes may confuse the clinical picture.
Suprapatellar Bursitis is usually the result of direct trauma to the suprapateliar bursa from either acute injury or repeated microtrauma.
SIGNS AND SYMPTOMS
Physical examination may reveal point tenderness in the anterior knee just above the patella. Passive flexion as well as active resisted extension of the knee will reproduce the pain. Sudden release of resistance during this maneuver will markedly increase the pain. There may be swelling in the suprapatellar region with boggy feeling to palpation. Occasionally the suprapatellar bursa may become infected with resulting systemic symptoms, including fever and malaise, as well as local symptoms, including rubor, color and dolor.
Due to the unique anatomy of the region, not only the suprapatellar bursa but also the associated tendons and other bursae of the knee can become inflamed and confuse the diagnosis. The suprapatellar bursa extends superiorly from beneath the patella under the quadriceps femoris muscle and its tendon. The 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 after overuse, misuse, or direct trauma. The quadriceps tendon is made up of fibers from the four muscles that compose 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 to form the medial and lateral patella retinacula, which help strengthen the knee joint. These fibers are called expansions and are vulnerable to strain, and the tendon proper is subject to the development of tendinitis. The suprapatellar, infrapatellar, and prepatellar bursae may also concurrently become inflamed with dysfunction of the quadriceps tendon. It should be remembered that anything that alters the normal biomechanics of he knee can result in inflammation of the suprapatellar bursa.
A short course of conservative therapy consisting of simple analgesics, nonsteroidal anti-inflammatory drugs, or cycloocygenase-2 inhibitors and a knee brace to prevent further trauma is a reasonable first step in treatment of patients suffering from suprapatellar bursitis. If the patient does not experience rapid improvement, the following injection technique is a reasonable next step. The goals of this injection technique are explained to the patient. The patient is placed in the supine position with a rolled blanket underneath the knee to gently flex the joint.
The described injection technique is extremely effective in the treatment of pain secondary to suprapatellar bursitis. The use of physical modalities including local heat as well as gentle range of motion exercises should be introduced several days after the patient undergoes this injection technique for suprapatellar bursitis pain. Vigorous exercises should be avoided as they will exacerbate the patient’s symptomatology. Simple analgesics and nonsteroidal anti-inflammatory drugs may be used concurrently with this injection technique.