There are multiple bursas around the knee. The most important of them are the prepatellar bursa, infrapatellar bursa and pes anserine bursa. These are most commonly involved in the inflammation and the swelling. They can be caused due to daily activities like kneeling or may be caused due to pathology in the knee leading to bad biomechanics around the knee.
They can be treated usually with RICE that is rest, ice, compression and elevation along with anti-inflammatory medications. They can also be treated with cortisone shot if not improved. The patient should see a physician if the pain is not relieved with over-the-counter medications.