the next most common cause There is no consensus on the need for parenteral versus oral antibiotics The prepatella bursa and olecranon bursa are most commonly infected Bursae are located throughout the body, but bursitis occurs only in a few Prepatella bursitis, commonly called “housemaid’s knee” results from frequent or prolonged kneeling Pes anserinus bursitis occurs on the lateral aspect of the knee where the tendons of the hamstring muscles overlie the tibia Retrocalcaneal bursitis occurs between the calcaneus and Achilles tendon, and is often caused by direct pressure from ill-fitting footwear or high-heeled shoes Olecranon bursitis most often results from a single direct blow to the elbow Shoulder or subacromial bursitis is often associated with calcifications and produces severe pain with abduction Other commonly affected bursae include the inferior calcaneal bursa and the trochanteric bursa An unusual form of bursitis is known as a popliteal or Baker cyst This occurs in the bursa that cushions the tendons of the gastrocnemius and semimembranous muscles from the distal femur The presence of this condition in adults is highly suggestive of intra-articular knee damage In children with a Baker cyst, there is frequently a congenitally wide opening joining the bursa sac with the knee joint itself One-way flow of synovial fluid into the bursa produces swelling just below the popliteal fossa on the medial side Patients with chronic inflammatory conditions of the knee, such as JIA, are at increased risk of developing popliteal cysts In children, the cyst frequently comes to medical attention as an asymptomatic mass behind the knee The swelling may limit full flexion of the knee and produces the sensation of tension with extension The mass is typically nontender and transilluminates Presence of an associated knee effusion is unusual and suggests the need for further evaluation of intra-articular knee pathology Ultrasound is the preferred imaging technique in children as it can distinguish the fluid-filled popliteal cyst from other solid masses Ultrasound is noninvasive, avoids ionizing radiation, and can identify even small cysts MRI is more accurate than ultrasound but not as essential in children, given the significantly lower incidence of accompanying intra-articular injury Rarely, an arthrogram or bursagram may be used to outline the cyst, document the articular connection, and detect ruptures of the cyst Bursa inflammation produces swelling and localized tenderness with direct palpation Any movement of the tendons overlying the site will reproduce the pain Conservative therapy consisting of restricted activity, frequent application of ice, and regular use of nonsteroidal anti-inflammatory medications is successful